West Virginia authorities are still searching for four miners who went missing in the aftermath of a deadly mining blast that killed 25 people at a coal mine Monday afternoon.

Believed to be the worst U.S. mining disaster in more than 25 years, the blast at the Upper Big Branch mine occurred at about 3 p.m., while 31 workers were in the midst of a shift change. A build-up of methane gas is the suspected cause of the explosion at the mine, which is located about 48 kilometres south of the state capital of Charleston.

So far, the bodies of 11 miners have been recovered, CNN's Sandra Endo told CTV on Tuesday, the day after the disaster.

Efforts to locate the four missing miners have been stalled by a build-up of methane gas in the areas where rescuers intend to search.

Rescuers plan to drill a 300-metre hole into the earth to release methane gas before they attempt to locate the missing miners. But they need to bulldoze an access road before drilling the hole.

Joe Manchin, the state governor, told an early morning news conference that it would take at least 12 hours to get the rescuers back into the mine, an event he predicted was unlikely to occur before 6 p.m. ET.

"It's going to be a long day and we're not going to have a lot of information until we can get the first hole through," Manchin said.

It is believed that the four missing miners are unlikely to have survived.

"All we have left is hope and we're going to continue to do what we can," Kevin Stricklin, an administrator with the U.S. Mine Safety and Health Administration, told a news conference.

"But I'm just trying to be honest with everybody and say that the situation does look dire."

Stricklin said a group of miners leaving the mine felt a blast of air and turned back to investigate what was happening. When they returned, they found nine others, seven of whom were dead. Additional mine workers were hurt or missing inside the mine.

Miner Steve Smith was inside the mine at the time of the blast, but escaped with his life.

"Before you knew it, it was just like your ears stopped up, you couldn't hear and the next thing you know, it's just like you're right in the middle of a tornado," Smith told ABC's Good Morning America.

Endo said eyewitness reports suggested the blast "took you off your feet."

"In one account, this man was getting out of the mine taking his shirt off and he was watching his son, his nephew and older brother go in to work their shift," she told CTV's Canada AM from Marsh Fork, West Virginia, on Tuesday morning.

"The blast blew his shirt off and those three of his relatives, unfortunately, did not make it and were part of those who were identified. Those are the types of stories that we're hearing and we know that there are certainly more to come."

Among the dead were 62-year-old Benny R. Willingham, a 30-year miner who was only five weeks from retirement, said his sister-in-law, Sheila Prillaman. He was supposed to take a cruise with his wife next month.

Prillaman said the family learned of his death after seeing his name on a list of victims posted by the company.

Willingham's daughter, Michelle McKinney, heard about her father's death from a local official at a nearby school.

"They're supposed to be a big company," Willingham said. "These guys, they took a chance every day to work and make them big. And they couldn't even call us."

Diana Davis said she lost her husband, 51-year-old Timmy Davis, along with two of his nephews, 27-year-old Josh Napper and 20-year-old Cory Davis.

At an Easter prayer breakfast in Washington, U.S. President Barack Obama asked the audience to pray for the people who died in the tragic accident at the mine. He said the government will help the state with whatever it needs.

The U.S. Secretary of Labour, Hilda L. Solis, said the U.S. Mine Safety and Health Administration will "investigate this tragedy and take action."

"Miners should never have to sacrifice their lives for their livelihood," Solis said in a statement.

The blast at the Massey Energy Company-owned mine is believed to be the deadliest since a fire killed 27 people at the Emery Mining Corp.'s mine in Orangeville, Utah, in 1984.

In 1970, a blast at the Finley Coal Mine in Hyden, Kentucky, killed 38 people.

Massey Energy Company, the owner of the West Virginia mine, is a publicly traded company that owns 2.2 billion tons of coal reserves in the region.

Don Blankenship, the chairman and CEO of Massey Energy, offered his condolences to the miners through a statement that was released early Tuesday morning.

"Tonight we mourn the deaths of our members at Massey Energy," Blankenship said.

In the past year, the company was fined US$382,000 for repeated serious violations involving its ventilation plan and equipment at the West Virginia mine where the blast occurred.

With files from The Associated Press