US President Obama: "There are rescue teams searching tirelessly"
Twenty-five miners are now known to have died and four are missing in an accident at a West Virginia coal mine.
The worst mine disaster in the US since 1984 was caused by an underground explosion at Upper Big Branch, about 30 miles (50km) south of Charleston.
It happened at about 1500 (1900 GMT) in a chamber 330m (1,000ft) below ground, mine owner Massey Energy Company said.
The rescue operation has been suspended because rising methane gas levels have heightened the risk of another blast.
The operation will resume as soon as conditions allow, Massey Energy said.
There are plans to drill boreholes from the surface to monitor gas levels and attempt to ventilate the mine chamber.
A mine safety official said rescue teams had reached one of the mine's airtight chambers stocked with food, water and oxygen but found no-one there.
US President Barack Obama offered his "deepest condolences" to the families and friends of those who had died.
"The federal government stands ready to offer whatever assistance is needed in this rescue effort," he said at a White House Easter prayer breakfast.
Monday's explosion happened as 29 workers were in a vehicle transporting them out of the mine during a shift change.
Miners in a vehicle ahead felt a blast of air and went back to find out what happened, finding several people dead and two injured.
The farther we got down the track, the more the wind picked up and... before you knew it, it's like your ears stopped up, you couldn't hear and the next thing you know, you're in the middle of a tornado
Rescuers had been trying to reach trapped miners further into the mine, but some of them also appear to have been found dead.
Four miners remain unaccounted for, but officials said there was not much hope of finding them alive because none had reached a rescue chamber.
"The situation is dire," Kevin Stricklin, an administrator for the federal Mine Safety and Health Administration, told a news conference.
Steve Smith, who was entering another part of the mine several miles away at the time of the blast, said dust was lingering in the air.
"The farther we got down the track the more the wind picked up and... before you knew it, it's like your ears stopped up, you couldn't hear, and the next thing you know, you're in the middle of a tornado," he told MetroNews.
"Since we weren't that far underground... we just hurried up and high-tailed it back to the outside."
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
1970 - 38 killed in explosion at Hyden, Kentucky
1968 - 78 killed in explosion at Farmington, West Virginia
1907 - 362 killed in explosion at Monongah, West Virginia
One of those killed, Benny Willingham, was 62 years old and only five weeks away from retiring, his sister-in-law Sheila Prillaman said.
The mother of another miner described how she had first heard about the accident.
"I just started getting all these phone calls. They asked me if Kevin was working the evening or day, that's all they said. When I told him 'evening'... they told me there had been an explosion," Jenny Waycaster told the Associated Press.
Gov Manchin told reporters overnight that seven bodies had so far been recovered and identified, but the other 18 had not.
"The families want closure. They want names. They understand the challenges. Right now I told them to do what they do best. Love each other and come together as a family," he added.
Sheri McGraw of the American Red Cross said the gathering of families awaiting news was "the most horrifying thing I've ever seen".
Relatives and neighbours talk of their grief and fears
State mining director Ron Wooten said that although the situation did not seem promising, rescuers had not "given up hope at all".
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 (£251,700) for serious violations at the mine over the past year.
There have been three fatalities there since 1998 - two from roof collapses and one from electrocution - according to the Associated Press.
Last year, 34 miners were killed in accidents across the US, the lowest on record.
But Monday's accident is the deadliest since 1984, when 27 people were killed by a fire at Emery Mining Corp's mine in Orangeville, Utah.
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