Twenty-five miners are now known to have died and four are missing after an accident at a West Virginia coal mine.
The accident was caused by an underground explosion at the Upper Big Branch mine some 30 miles (50 km) south of Charleston in the eastern US. The blast happened around 1500 (1900 GMT), said the mine's owner Massey Energy Company.
The number of fatalities makes this the worst US mine disaster since 1984. Rescue efforts have been suspended.
Safety officials said rising methane gas levels had heightened the risk of another explosion.
The operation would resume as soon as conditions allowed, Massey Energy said.
There are plans to drill a borehole from the surface to try to reach the missing men.
"We are sending all of our prayers and thoughts to the brave miners and their families," said West Virginia Senator Jay Rockefeller.
"I just spoke with President Obama and he has promised to make every asset available to help us and we will be in contact as the rescue continues," said West Virginia Governor Joe Manchin.
"We are all working diligently together and I ask that everyone pray for the miners, their families and our rescue teams."
Trapped teams
The blast happened as a number of workers were in a vehicle transporting them out of the mine.
 | US MINE DISASTERS Jan 2006 - 12 killed in methane explosion at Sago mine, Tallmansville, West Virginia 2001 - 13 dead in explosions in mine at Brookwood, Alabama 1989 - 10 killed in explosion at Wheatcroft, Kentucky 1984 - 27 killed in fire at Orangeville, Utah 1968 - 78 killed in explosion at Farmington, West Virginia 1907 - 362 killed in explosion at Monongah, West Virginia  |
Rescuers had been trying to reach trapped miners further into the mine, but some of them also appear to have been found dead.
Officials say four miners are still unaccounted for, but there was not much hope of finding them alive as they did not appear to have reached chambers which could have provided them with extra oxygen.
"It does not appear that any of the individuals made it to a rescue chamber," Kevin Stricklin, an administrator for the federal Mine Safety and Health Administration, said at a news conference.
"The situation is dire."
Earlier reports suggested that some of the miners may have survived, evoking memories of the Sago mine disaster in the same state in 2006 when 13 miners trapped for 42 hours were declared to be still alive, only for 12 of them to be found dead.
Massey Energy says on its website that it has a safety record that is above the national average, with three fatalities in the last 12 years.
But federal inspectors have fined the company more than $382,000 for serious violations at the mine over the past year, the Associated Press reports.
Last year 34 miners were killed in accidents across the US, the lowest on record.
But the Upper Big Branch accident is the biggest since 1984, when 27 people were killed by a fire at Emery Mining Corp's mine in Orangeville, Utah.
BBC NEWS
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