MONTCOAL, W.Va. (Reuters)—An explosion ripped through a West Virginia coal mine owned by Massey Energy on Monday, killing at least 25 miners in the deadliest U.S. mining disaster since 1984.

West Virginia Gov. Joe Manchin said on Tuesday morning that four miners remained missing deep underground and that 11 of the dead had been identified. "You can imagine the anxiety for the family members," Gov. Manchin told the CBS "Early Show."

The explosion occurred Monday afternoon at the Upper Big Branch Mine in Montcoal, about 30 miles south of the state capital of Charleston.

The mine, owned by Massey’s Performance Coal subsidiary, has two emergency chambers stocked with food, water and enough air to survive for four days, and rescuers were still hoping the missing miners had made their way there.

“This is still a rescue operation,” said Kevin Stricklin of the U.S. Mine Safety and Health Administration. "We can't give up hope at all. All we have left is hope."

But about 50 rescuers were forced to pull back from the search area earlier because methane gas and smoke underground made it too hazardous to continue the search.

The high concentration of gases suggests there may have been a second explosion, Mr. Stricklin said.

Gov. Manchin said he didn't know enough about the mine’s safety record. Asked about the fines it has faced over improper ventilation of methane, Gov. Manchin told CBS, "Yeah, I've heard that. And we'll just have to find out. There's no excuse.”

Rescuers intended to drill a borehole from the surface above the mine to try to reach the missing men.

Gov. Manchin said drilling had begun on Tuesday but it would be close to evening before rescuers reach their target of 1,100 feet.

The death toll makes it the deadliest U.S. mining disaster since 1984, when 27 miners died in a fire in Utah, according to the United States Mine Rescue Assn.

Massey CEO Don Blankenship said the company was "taking every action possible to locate and rescue those still missing."

Massey, headquartered in Richmond, Va., is the largest coal producer in Central Appalachia, with operations in West Virginia, Kentucky and Virginia.

Massey said on its Web site that its accident rate fell to an all-time low for the company in 2009. It said its safety record last year was stronger than the industry average for the sixth consecutive year.

But according to federal records, the Upper Big Branch Mine has had three fatalities since 1998 and has a worse-than-average injury rate over the last 10 years. Two of the miners died in roof collapses in 1998 and 2001, while a third was electrocuted in 2003 when repairing an underground car.

Ellen Smith, the editor of Mine Safety and Health News, said the Upper Big Branch mine had been repeatedly cited for safety violations going back years and continuing this year.

The mine, which employs just over 200 people, uses the "longwall mining" method to tear coal from a lengthy face, leading the ground behind it to collapse. Critics say the method can cause surface subsidence and damage to buildings.

In the worst coal mine disaster in U.S. history, 362 miners died in an explosion in 1906 in West Virginia's Monongah mine.

In January 2006, 12 miners died after an explosion in the Sago Mine, run by International Mines Corp. in Tallsmansville, West Virginia, according to the U.S. Mine Rescue Assn.