Rescue crews found one body late Tuesday in a West Virginia mine where 13 miners were trapped for nearly two days after an explosion, but they held out hope that the others were still alive, even as precious time continued to slip away.

The unidentified body was found about 700 feet from a mine car, and it appeared the employee was working on a beltline, which brings coal out of the mine, said Ben Hatfield, chief executive officer for the mine's owner, International Coal Group Inc. of Ashland, Ky.

Red Cross volunteer Tamila Swiger, who was with miners' families inside a church, said family members were "passing out and crying and just really in bad shape" after hearing about the body.

There was no immediate word about the fate of the other 12 miners, who had been trapped for more than 39 hours 260 feet below the surface of the Sago Mine, about 100 miles northeast of Charleston.

Gov. Joe Manchin said that fresh rescue crews were brought in late Tuesday night to continue searching for the workers in a mine he said was "extensive" in size, despite poor air quality that he said stacked the odds against a happy ending.

"They're doing everything humanly possible," he said. "We know that they are together somewhere and we're trying to find those 12 miners. It's still an uphill battle."

Manchin said the rescue operation "will be longer than we anticipate," but he did not say how long.

Rescuers located the body about 11,250 feet from the mine's entrance. Officials had thought the miners were about 12,000 feet inside the mine.

Hatfield said it appeared that the other miners were able to get out of the mine car "under their own power."

"But we do not know from there, at this point, where they have gone," he said. "We are still operating in rescue mode and are looking for survivors."

Rescuers cannot go any farther into the mine without improved ventilation systems, which the company was installing, he said.

Company officials have refused to speculate on the cause of the blast, but the governor's office said it might have been caused by lightning.

Hatfield said rescue crews did not find a cave-in or a roof collapse in the mine. He said the explosion may have occurred in an abandoned section of the mine that was sealed off in December.

Manchin said the abandoned section did not have equipment "back there that could make it (the explosion) happen."

Sandy Barron, whose nephew Randal McCloy was one of the trapped miners, said families were told there was no trace of the other men. And they were still hopeful their loved ones made it to safety.

Families hoped the fact that the mine car was undamaged meant the other miners may have been able to escape unharmed.

"There's a very good chance they've barricaded themselves somewhere," said John Groves, whose brother Jerry Groves was among the trapped miners. "They don't know where they went, but they went somewhere."

Earlier Tuesday, the prospects of finding any of the miners alive appeared bleak after holes drilled into the ground yielded deadly levels of carbon monoxide and no signs of life.

"With each hour that passes, the likelihood of a successful outcome diminishes," Hatfield said, adding that the rescue effort was "clearly in the situation where we need a miracle."

Rescue teams worked their way through the mine on foot for fear machinery might cause volatile gases to explode.

The company told families that a powerful explosion had rocked the mine, based on damage near where the miners may be trapped, said Rick McGee, who works at the mine with McCloy, his brother-in-law.

Cinderblock walls meant to direct the flow of air inside the mine were knocked down by the blast, McGee said.

Given the new information, McGee said, "There's a chance, not a great chance, but there is still a chance" that the miners could still be alive if they were able to barricade themselves.

President Bush said the nation was praying for the men, and he offered federal help to bring them out alive. "May God bless those who are trapped below the earth," he said.

Rescuers had drilled narrow holes into the mine, inserted air monitors and found levels of carbon monoxide more than three times the maximum regarded as safe. Carbon monoxide, a byproduct of combustion, can be lethal.

Hatfield said it was possible the miners barricaded themselves somewhere and were still alive. But, he said, company officials were "very discouraged" by the test results.

Also, a camera lowered down a 6 1/4-inch hole spotted no sign of the miners, and drilling crews pounded on a steel pipe and listened for a response but heard nothing, Hatfield said.

Family and friends of the miners had been gathering at the church since word first spread of the explosion. On Tuesday they prayed, sang hymns and got periodic briefings from the company and Manchin.

The governor knows first hand what it's like to lose loved ones in a mine accident. His uncle and several friends were among 78 miners killed in an explosion at a coal mine in Farmington, in Marion County, in 1968. The accident spurred Congress to pass the Coal Mine Health and Safety Act the following year.