Tallmansville - A coal mine explosion that may have been sparked by lightning trapped 13 miners 260 feet below ground Monday, and rescuers went in to find them after waiting almost 12 agonizing hours for dangerous gases to clear.

The condition of the miners was not immediately known. Four co-workers tried to reach them but stopped because of contaminated air, and the blast knocked out the mine's communication equipment, preventing authorities from contacting the miners.

It was not known how much air they had or how big a space they were in. The miners had air-purifying equipment but no oxygen tanks, a co- worker said.

"You just have to hope that the explosions weren't of the magnitude that was horrific from the beginning," Joe Manchin, governor of the nation's No. 2 coal-producing state, told CNN. He added: "There's always that hope and chance that they were able to go to part of the mine that still had safe air."

The first of eight search-and-rescue teams entered the Sago Mine, more than 11 hours after the blast trapped the miners and reported making steady progress. Rescue crews were kept out of the mine for most of the day while dangerously high levels of carbon monoxide _ a byproduct of combustion _ were vented through holes drilled into the ground, authorities said.

Company officials believe the miners were about two miles inside the mine, about 260 feet under the ground. The crew entered the mine on foot for fear of sparking another explosion.

Roger Nicholson, general counsel for the mine's owner, International Coal Group, said late Monday that mine officials had not heard from the trapped miners since the explosion 16 hours earlier.

Officials refused to estimate how long it would take to reach the miners. The company was drilling a six-inch hole at the explosion site that would allow it to monitor air inside the mine and drop a listening device. They expected to need four to six hours to complete the drilling.

Gene Kitts, a senior vice president at ICG, described the rescue effort as "a very slow, very careful, methodical process."

The federal Mine Safety and Health Administration sent a rescue robot to the mine, about 100 miles northeast of Charleston.

Some 200 co-workers and relatives of those trapped gathered at the Sago Baptist Church, across the road from the mine.

Anna McCloy said her husband, Randall, 27, was among those missing. She said he had worked at the mine for three years "but was looking to get out. It was too dangerous."

Coal mine explosions are typically caused by buildups of naturally occurring methane gas, and the danger increases in the winter months, when the barometric pressure can release the odorless, colorless and highly flammable gas.

Lara Ramsburg, a spokeswoman for the governor, said the blast may have been sparked by lightning from severe thunderstorms.

Nicholson, general counsel for ICG, said that it was not clear what caused the blast and that there was no indication it was methane- related.

The mine had been idle over the weekend for the New Year's holiday, and two groups of miners were to resume production on Monday. A "fire boss" went into the mine before the first group entered the mine at 5:51 a.m. and declared it safe.

"That just adds to the mystery of what happened when the production crew went underground," Kitts said.

The second group of miners entered at 6:30 a.m., just before the explosion knocked out power in the mine. The second group withdrew.

The mine has a single entrance, and the shaft winds its way for miles underground. The miners were supposed to be working about 160 feet below the surface, said the wife of one of the trapped men.

But it was unclear how far into the shaft they had gone when the blast struck.

Kitts said if the miners reached the section where they were headed, they would be 10,000 feet from the mine's entrance.

"If the miners are barricaded, as we hope they are, they would prepare themselves for rescue by rationing," Kitts said. The miners would probably have only their lunches and water on hand.

"These miners are experienced, they are well-trained," Kitts said. "We are just praying they had an opportunity to put their training to use."

The miners had three to 30 years of experience working in the mining industry, Kitts said. The company declined to release their names.

Samantha Lewis, whose 28-year-old husband, David, was among those trapped, said he worked the mines so that he could be home every night to take care of their three daughters while she worked on a master's degree in health care administration.

"This was a good way to make a living until we could find something else," said Lewis, whose father, grandfather and stepfather also worked in the mines. "It's just a way of life. Unless you're a coal miner or you have a college degree, you don't make any money."

Miners who work in the mine carry individual air purifying systems that would give them up to seven hours of clean air, said Tim McGee, who works at the mine and was among those at the church. They do not carry oxygen tanks, he said.

"What I want to hear is he is alive, but they can't tell me that," said Loretta Ables, whose fiancee, 59-year-old Fred Ware Jr., was one of the trapped miners. "He's worked in this mine for six years. He said that's the way he's gonna go _ in the mines."

Another trapped miner, 61-year-old Jim Bennett, planned to retire this year, said his son-in-law Daniel Merideth.

"Every day he would come home and pray for who was going in," said Merideth, who stood outside the mining complex. "Right now, he is probably in there witnessing to people. He would be organizing and praying."

ICG acquired the Sago Mine (pronounced SAY-goh) last March when it bought Anker West Virginia Mining Co., which had been in bankruptcy. In 2004, the latest year for which figures are available, the Sago Mine produced about 397,000 tons of coal.

Federal inspectors cited the mine for 46 alleged violations of federal mine health and safety rules during an 11-week review that ended Dec. 22, according to records.

The more serious alleged violations, resulting in proposed penalties of at least $250 each, involved steps for safeguarding against roof collapses, and the mine's plan to control methane and breathable dust. The mine received 208 citations from MSHA during 2005, up from 68 citations in 2004.

The state Office of Miners' Health Safety and Training issued 144 notices of violation against the mine in 2005, up from 74 the year before.

West Virginia ended 2005 with three mining deaths, the lowest since 2000.

Last year, 22 coal miners were killed on the job in the United States, a record low, according to Suzy Bohnert, spokeswoman for the U.S. Mine Safety and Health Administration. The previous record low was 27 in 2002.

In February 2003, three contract workers were killed by a methane explosion while drilling an air shaft at a Consol Energy coal mine near Cameron.

In September 2001, 13 coal miners were killed in a series of explosions at a mine in Broached, Ala. That was the nation's worst mining accident since 1984, when fire killed 27 coal miners near Orangeville, Utah.

In July 2002, nine coal miners were rescued after being trapped for 77 hours in a mine near Somerset, Pa.

The deadliest coal mining disaster in U.S. history was an explosion in 1907 in Monongah, W.Va., that killed 362 people.