Hopes are fading of finding more survivors after the worst US mining disaster in two decades killed 25 miners, with rescuers forced to pull back fearing a new methane blast.
Four miners were still missing and feared dead in Montcoal, West Virginia after Monday's deadly explosion set off a fireball which tore through the Upper Big Branch mine operated by a unit of Massey Energy Company.
A build up of lethal gases forced rescuers to the sidelines Tuesday, waiting for crews to drill holes into the side of the coal mine to release the toxic air.
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"Rescue teams have been called back because of the amount of methane in the mine," West Virginia mining agency spokesman Hoy Murphy told AFP.
Massey chief executive Don Blankenship told West Virginia MetroNews radio he did not know when the rescue operation would resume as it was not yet certain that the first drill holes at the mine would work.
"There are a couple of possibilities to clear up the explosive atmosphere, but I think I would be negligent to say when that all is going to happen," Blankenship said.
Mixed feelings on rescue
"I don't have a lot of hope that they're alive," he added. "We always have hope but given ... the appearance of the explosion that was described by some of the rescue team members that I talked to I don't give it much hope."
West Virginia Governor Joe Manchin said survivors had described their shirts being blown off by the force of the blast, which turned rail lines and heavy equipment into bent and twisted wreckage.
Obama's condolences
As relatives of the four missing workers faced an agonizing wait for news, US President Barack Obama sent his "deepest condolences" and "prayers" to the families and the close-knit mining community.
Authorities were clinging to slim hopes the workers could have reached a rescue chamber with clean air, food and water to last 96 hours. The bodies of 19 workers were still in the mine and two injured remained in hospital.
"Most people are saying that they just don't believe it. We lost so many good guys," pastor Tobie Hilderbrand told AFP. "The mine is a way of life for most of the people in this area... everyone is affected."
Investigation launched
As investigators probed the cause of the giant fireball, West Virginia Senator Jay Rockefeller said he would visit the mine to oversee the rescue effort and investigate what happened.
"We will leave no stone unturned in determining how this happened and in taking action for the future," he said in a statement.
The accident, the worst US mining mishap since 1984, hit Monday afternoon during a shift change at the mine, located some 30 miles (50 kilometers) south of the state capital Charleston.
The facility is run by Performance Coal Company, a subsidiary of Massey Energy, the fourth biggest coal producer in the US which operates some 50 mines across the country.
Established during the 1920s by a powerful Virginia industrial family of the same name, Massey produces 40 million tonnes of coal each year. It is valued at some $2.3 billion and had 2009 earnings of $104 million.
The company maintained that its top priority was "the safety of our miners and the well-being of their families."
Mine owner cited for 'dangerous conditions'
The mine owner and operator have been cited repeatedly for potentially dangerous conditions, including high levels of combustible methane gas and Massey paid out more than $4.2 million in criminal and civil fines last year.
But Blankenship said: "Any suspicion that the mine was improperly operated or illegally operated or anything like that would be unfounded."
Other violations in recent weeks include cracking and collapsing of mine wall, ventilation problems and inadequate air quality, according to federal government records.
Coal mining is one of the key industries in West Virginia producing 165 million tonnes each year, an amount in coal production second only to the western US state of Wyoming.
In the last major mine explosion, in January 2006, 12 people died in a Sago, West Virginia, coal mine, owned by the International Coal Group, after they were trapped by an explosion 80 meters (260 feet) underground. One miner survived.
The worst US mining disaster ever was in 1907 in Monongah, West Virginia, where an explosion killed 362 workers.
The United Mine Workers of America said it had dispatched trained staff to the site to help, even though it was non-unionized.
"We are all brothers and sisters in the coalfields at times like this," said union president Cecil Roberts.
