When a series of monstrous explosions shook inland Waverley one July afternoon, farmer Jim Ross thought a plane had crashed.

The big bangs happened on July 7, 1999, just after 4pm, and a report on the unusual astral event was issued last month by Jennie McCormick of Auckland's Stardome Observatory.

The phenomenon was caused by a meteor - a piece of rock left over from the formation of planets - entering Earth's atmosphere.

Just after 4 o'clock on that July day, Mr Ross had stopped his motorbike on Kohi Rd, about 4km inland from Waverley, to talk to a neighbour.

"Firstly I heard a big bang, then a whole lot of crinkling noise like someone screwing up silver paper.

"The next thing I remember was a monstrous bang, a huge explosion. It was just unreal."

The shed where his daughter was milking shook and his dogs "went practically straight through a boxthorn hedge". Through the cloudy sky above him came blue smoke, which hung around for about two hours.

He rang the Wanganui police and told them about the explosion.

They were inundated with 111 calls, and went searching as far as Waverley, Waitotara and Brunswick.

"The next moment the Waverley fire brigade trailed by with about 30 cars behind it. They were going up the road expecting to find a plane crash," Mr Ross said.

A kilometre north-west of Waverley, farmer Grant Hughes was riding his quad bike just after four on that afternoon. He saw a bright flash in the sky, followed by a huge explosion.

"The pressure waves from the explosion physically forced me hard down on to the bike, not once, but twice. I have never known or felt anything like it," he said later.

Other Wanganui and South Taranaki observers reported a smoky, sulfurous smell, terrified animals, earth tremors and heat hazes.

A pair of Mowhanau Beach walkers found live shellfish at the water's edge three days later, which may have been related to the pressure changes caused by the explosions.

They were seen by people from Auckland to Nelson and more than 100 people, from Northland to Canterbury, saw the meteor shoot southward across the sky. They described it as a bright silver/yellow/red/orange/blue/violet/black object with a long, fiery tail.

The explosion was described as a flash of blinding light from which a vivid blue-and-white compact cloud emitted leaf-like objects.

The cloud hung in the sky for at least 40 minutes.

Staff from the Auckland observatory came south to interview people who had seen the meteor explode, and Mr Ross helped them to find witnesses. There were 115 written reports, audio and videotape and seismic records.

The United States Defence Support Programme also recorded information, but says this is classified.

The Chronicle published a photograph taken by Gordon Gwilliam, of Wanganui.

Waverley dairy farmer Greg Brown had a T-shirt printed, and Waverley's Clarendon Hotel held a meteorite night and invented a new drink.

Mr Ross has been sent a copy of the observatory's final report. He supplied it to the Chronicle and wanted to share its findings with local people who saw the fireball. The astronomers at the observatory were deeply envious of the experience, he said.

He was told: "You people down here don't really comprehend what you've heard and seen. People like us would give our lives to see something like that."

The observatory's report became the cover story in an international journal.

It says there has only been one other daylight fireball with lots of witnesses. That was in January 1996 and there were no reports of it exploding.

Similar incidents at twilight and at night occurred in New Zealand in 1933 and 1929.

"The Taranaki Fireball is the only fireball to have been observed and reported by numerous witnesses across the North and South Islands of New Zealand," the report says.

Those observations, with seismic records, enabled astronomers to pinpoint a few facts about what happened.

They concluded that the meteor entered Earth's atmosphere northeast of the North Island. Its speed has not been determined, but was probably as high as 15km per second.

It detonated in a series of three explosions at 4.14pm, at a height of about 32km.

According to the report, the detonation happened approximately above Rawhitiroa, about 8km east of Eltham.

The explosion is estimated to have had the energy of at least 300 tonnes of TNT.

The sonic boom was heard as far away as Turangi and Bulls and variously described as like artillery fire, hissing, backfiring or rumbling thunder.

The seismic shockwave was equivalent to an earthquake measuring about 3.9 on the Richter Scale.

After the event, scientists and citizens searched for fragments of the meteor, said to possibly look like burnt egg shells and be worth up to $50,000.

Nothing was ever found, and the explosion may have reduced whatever was left of the space rock to powder.