Clark T. Colvin, a spokesman for Huntsman, said all plant personnel were safely evacuated.

The cause of the blast was not immediately determined.

The evacuation request was issued to residents of the city's El Vista area. "It's a precautionary measure," said police Sgt. Janice Marshall.

The request was lifted just before 4 p.m.

Officials said the blaze was under control, but it was unknown Saturday afternoon whether the fire had been extinguished.

Google specifically bars Web addresses that infringe on trademarks from using its ad network, but a review of placeholder Web sites that result from misspelled domain names of well-known companies found many of the ads on those pages come directly from Google.

"It seems very hard to reconcile Google's support of this activity with their 'Do No Evil' motto," said Ben Edelman, a Harvard University researcher who has looked extensively into advertising on unused domains.

Google is defending its business practices, saying it removes participating sites from its ad network if a trademark owner complains those sites are confusingly similar.

"Unless it is confusing to somebody, trademark law doesn't apply," said Rose Hagan, Google's chief trademark lawyer.

The Silicon Valley search giant is the largest but not the only ad network showing ads on placeholder Web pages. Yahoo! and Australian firm Dark Blue Sea run similar services.

This form of online advertising relies on "type-in traffic": users who type the information they're looking for into the Web browser's address bar instead of using a search engine. Industry analysts estimate 15 percent of Web traffic originates this way.

That has created a demand for domain parking, which involves owners of a domain name "parking" that name with a firm that creates placeholder pages and then inviting Google or other Internet ad networks to fill them with ads.

When Web surfers arrive at those sites and click on those ads, Google and Yahoo! get paid by advertisers for that click and share their revenue with the owners of the domain names.

Opinion about these ad pages is divided. Some say they are frustrating junk pages. Others, including those who speculate on potential traffic of a specific domain name, say they help people find information related to what they're looking for.

"We want those pages to function as alternatives to search engines," said Matthew Bentley, chief strategy officer for Sedo, a parking service that manages more than 1 million unused addresses placed with the Google ad network.

The parked ad pages are mostly unattractive, but Sedo, Google and Yahoo! said they are working to improve them by adding more information. The parking service usually handles the creation of the ad sites.

"It's such an easy process," said Ron Jackson, publisher of DNJournal.com, an online publication that covers the industry. "In two minutes, I can set up a thousand domain names."

The practice has sparked a speculative scramble to register unused names and test their ad potential. Because purchasers can change their minds within five days and avoid paying the $6 registration fee for the name, many investors enter the names in Google's ad program for a quick test and quickly drop those that don't yield enough clicks to cover the domain registration fee.

Of the 30 million dot-com names registered worldwide last month, more than 90 percent were dropped, according to domain name registrar GoDaddy.com. As a whole, the Internet has 54 million active .com and .net addresses, according to VeriSign.

Jackson said he has bought 6,600 domains and uses several ad services to earn revenue on them. "I know quite a few guys making over a million dollars a year from advertising on their domains," he said. "It's like a 24-hour money-printing machine."

David Steele, an intellectual-property lawyer at Christie, Parker & Hale and a professor at Loyola Law School in Los Angeles, said the practice amounts to someone making money off someone else's trademark without permission.

"Trademark law is designed to protect consumers so they can quickly identify what they want and get it," Steele said. "If everyone has to spend a whole bunch of time wading through all this look-alike crap online, then the value for Internet consumers is going to be seriously reduced."

John Meyers, general manager of Yahoo!'s ad service for parked domains, said Yahoo! is strict about weeding out addresses that violate its guidelines, which prohibit celebrity names, typos of trademarks and references to illegal activity.

Yahoo! developed a software filter to identify domain names in its network that violate those rules so they can be removed.

But Hagan, Google's trademark lawyer, said software formulas aren't smart enough to identify trademark infringements.

"It's subjective when you look at domain names to decide how many letters off does it have to be to form a trademark or conjure up that trademark," she said.

Google won't disclose how much it is earning from ads on these types of sites, but Chief Executive Eric Schmidt said last week, "It's a lot of money."

The company also doesn't break out how much it earns from ads on its own sites compared with partner sites, which include rival search engines such as Ask.com, thousands of news sites and blogs, and millions of vacant domains.

Wall Street analysts, however, estimate slightly less than half of Google's $6 billion in revenue last year came from ads shown on partner sites.

The Washington Post found hundreds of active Web sites showing Google ads at addresses that appear to be misspelled variations of well-known company names, known as "typo-domains." Their owners are known as "typosquatters."

The Post generated roughly 100 random misspellings of "www.earthlink.net" and found 38 sites using variations of the Earthlink name "parked" at a Google-owned service called Oingo.com. All 38, which includes "dearthlink.net" and "rearthlink.net," serve Google ads.

Likewise, nearly a dozen sites with variations of "Verizon Wireless" were showing Google ads, with some linked to the company's official VerizonWireless.com. That suggests Verizon Wireless may be paying Google for ads on typosquatter-owned sites.

Verizon Wireless spokesman John Johnson said the company has a successful track record of getting such sites shut down and takes "a particularly dim view of typosquatters."

"Do we think any traffic is good traffic as long as it ends up at our site? Clearly many of these sites are siphoning off traffic by tricking people ... This is never a good thing for our trademark or our company," he said.

That much capability would match the power of the best supercomputers from a decade ago - except those machines occupied as much as 50,000 cubic feet and required up to 50,000 watts of electrical power. The new technology - driven by a 90-nanometer Virtex-4 microprocessor developed by Xilinx Inc. of San Jose, Calif. - weighs only 40 pounds and requires only 80 watts of power.

"Our sensors on the Global Positioning System and Defense Satellite Program platforms have been severely constrained by the data downlinks available," said Mark Hodgson, NNSA's manager for space nuclear explosion monitoring. "This new reprogrammable supercomputing-payload technology enables our science staff to use in space the algorithms and methods previously only possible in ground-based mainframe computers, and to continually modify those methods in-situ, for better performance as science knowledge improves."

The new payload project "will be a path-breaker for our Space Nuclear Explosion Monitoring program," said W. Randy Bell, another NNSA manager, "enabling us to meet stringent new requirements for less weight and power, while growing our ability to discriminate nuclear-explosion-related signals versus natural and man-made background signals."

The test will be conducted aboard the Cibola Flight Experiment, due to be launched aboard a U.S. Air Force Atlas-V rocket in September from Cape Canaveral Air Force Station, Fla. Cibola, developed by SSTL of Surrey, England, comprises a reconfigurable processor payload intended for low-Earth orbit. It will survey portions of the VHF and UHF radio spectra.

The experiment will use a network of reprogrammable and field programmable gate arrays to process the received signals for ionospheric and lightning studies. The objective is to detect and measure impulsive events that occur in a complex background and would overload existing space-based computer systems.

The research partners said the technology also is aimed at boosting the power of Software-Defined Radio functions, a critical element of the military's tactical communications, and the system could be of great value to commercial television and radio broadcasting.

Along with the Virtex-4, the technology also draws on the AT697 RadHard SPARC processor by Atmel Corp., also of San Jose, Calif., and on the chalcogenide C-RAM by BAE Systems (formerly British Aerospace) of Farnborough, England.

HUNDREDS of dead dolphins have been washed up along the shore of a popular tourist destination on Zanzibar's northern coast, and scientists have ruled out poisoning.

It was not immediately clear what killed the 400 dolphins, whose carcasses were strewn along a four-kilometre stretch of Nungwi, said Narriman Jidawi, a marine biologist at the Institute of Marine Science in Zanzibar.

The public were warned against eating the dolphins' meat.

The bottleneck dolphins, which live in deep offshore waters, had empty stomachs, meaning they could have been disoriented and were swimming for some time to reoriente themselves. They did not starve to death and were not poisoned, Mr Jidawi said.

In the United States, experts were investigating the possibility that sonar from US submarines could have been responsible for a similar incident in Marathon, Florida, where 68 deep-water dolphins stranded themselves in March last year.

A US Navy taskforce patrols the East Africa coast as part of counter-terrorism operations.

The deaths are a blow to tourism in Zanzibar, where thousands of visitors go to watch and swim with dolphins.

"The administration has insisted it's not their job to fight global warming," said David Bookbinder, attorney for Sierra Club, which was joined in the suit by Environmental Defense and the Natural Resources Defense Council.

"In fact they have both the legal and moral responsibility to tackle global warming pollution," he said.

The states of California, Connecticut, Maine, Massachusetts, New Mexico, Oregon, New York, Rhode Island, Vermont, Wisconsin are parties to the suit filed in US District Court in Washington, as were the District of Columbia and New York City.

EPA does not regulate carbon dioxide, the most plentiful of the greenhouse gases, because the agency, on direction from the White House, does not consider it pollution, the groups said.

While carbon dioxide is not toxic -- humans exhale it in large quantities -- it does contribute to the so-called greenhouse effect, where certain gases in the upper atmosphere allow sunlight in, without allowing the heat to escape Earth, not unlike a greenhouse.

The greenhouse effect has always been with us, but scientists say that as cars and power plants release increasing amounts of gases like carbon dioxide, temperatures rise faster and have already begun to disrupt weather patterns.