HOPE was fading last night for 13 US coalminers missing after an explosion on Monday trapped them deep underground at the bottom of a two-mile mine shaft.

As toxic carbon monoxide gas reached dangerous levels, mining bosses were praying for a miracle. “With each hour that passes the likelihood of a successful outcome diminishes,” Ben Hatfield, the chief executive of the company operating the mine, said.

“We are clearly in the situation where we need a miracle. But miracles happen,” he added.

After frantic efforts by rescuers to reach the men, in an unfolding drama watched on television by millions of Americans, a hole was punched into the mine early yesterday — but it was a breakthrough that brought devastating news for the miners’ families.

Air tests taken in the West Virginia mine where the men are believed to have been at the time of the explosion revealed carbon monoxide far in excess of survivable levels.

Mr Hatfield announced that carbon monoxide levels measured 1,300 parts per million; the maximum level considered breathable is 400 parts per million.

“We are very discouraged by the results of this test,” he said. But he continued to hold out some hope, adding: “They could be at another location or they could be barricaded somewhere.”

After the air test, relatives of the men, who had been optimistic and talkative before the announcement, retreated into a nearby church in silence. Nick Helms, whose 50-year-old father, Terry, is among the trapped miners, called the news devastating.

The blast occurred at about 6.40am on Monday, trapping the men 260ft (80m) below the surface and nearly two miles from the mineshaft opening. The 13 workers had just entered the mine for the start of the first shift after the Christmas and new year holiday.

A second group of miners escaped after hearing the blast, which might have been caused by a build-up of methane gas that was then ignited by a lightning strike. Several of them tried to save their colleagues and reached 9,000ft down the gradually sloping shaft before air quality monitors indicated lethal levels of carbon monoxide.

Mr Hatfield said that rescuers on the surface pounded on the drill that bored the hole into the mine, but that there had been no response from underground. The uncertain fate of the men rapidly drew hundreds of television cameras and reporters to the scene, and was the dominant story across America throughout the day.

President Bush said that he had spoken to Joe Manchin, the West Virginia Governor, to tell him that “Americans across the country were praying for the men who were trapped”. Mr Bush added: “May God bless those who are trapped below the earth and may God bless those who are concerned about those trapped below the earth.”

As the families waited, troubling questions emerged about the mine’s safety record. According to the US Labour Department’s Mine Safety and Health Administration, the mine, near the town of Sago, received 208 health and safety warnings last year, up from 68 in 2004. The mine’s owner, International Coal Group — which took control of the mine last year — said the numbers were not extraordinary and most safety issues had been addressed. But investigators said they would review the records to see if any warnings had been ignored.

Cindy Burke told The Washington Post that one of the trapped men was a neighbour who had recently complained about the mine. She said that the man, Junior Hammer, walked into the town’s general store and asked for a cigar. “They said, ‘You don’t smoke’, and he said he didn’t know how much longer he was going to be alive because of the idiots at the mine,” she said.

Mr Hatfield said that when the camera reached the inside of the mine “no barricades or survivors were seen, but there was no evidence of substantial explosion damage”.

Rescuers were last night sending a robot into the main shaft. The drilling equipment being used was the same as that in the 2002 rescue of nine miners in Pennsylvania pulled to safety after 77 hours.

July 2002

Nine miners were rescued after being trapped in a Pennsylvania mine for three days

January 1959

Twelve died and sixty-nine were trapped for three days after a mine flooded in Jenkins Township, Pennsylvania

February 1943

Seventy-four miners and a rescue worker died in an explosion in Smith Mine, Montana

December 1907

An explosion in Monongah, West Virginia, killed 362 miners in America’s worst mining disaster

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