Holmes Mill, Ky. ? An underground explosion early Saturday in an eastern Kentucky coal mine killed five miners, while a sixth miner walked away from the blast that sprayed an office building with rock and mud 100 yards outside the tunnel’s entrance, Gov. Ernie Fletcher said.

The cause of the blast at the Darby Mine No. 1 in Harlan County was not immediately known. But Fletcher, who quickly flew to the scene, said preliminary evidence suggested methane might have leaked from a sealed-off portion of the mine, mixed with oxygen and then something caused it to ignite.

It was the deadliest mining incident in Kentucky since 1989, when 10 miners died in a western Kentucky mine blast, state officials said. The federal Mine Safety and Health Administration said the five deaths Saturday raised the national death toll from coal mining accidents to 31 this year, with 10 of the deaths in Kentucky.

The miners, who were part of a maintenance shift on duty when the blast occurred about midnight CDT, were found about 3,000 feet into the mine, said Ray McKinney, MSHA’s administrator for coal mine safety and health.

The governor said some of the dead miners had donned breathing devices after the explosion and tried to climb to safety. Federal investigators said four of the victims were found close together.

The only survivor, Paul Ledford, was closer to the mine’s exit than his co-workers who were killed, Fletcher said. He was about 15 feet from the mine’s exit when he came across rescuers, officials said.

Authorities identified the victims as Amon Brock, 51, of Closplint; Jimmy D. Lee, 33, of Wallins Creek; Roy Middleton, 35, of Evarts; George William Petra, 49, of Kenvir; and Paris Thomas Jr., 53, also of Evarts.