West Virginia Mine Explosion: The worst U.S. mining disaster in two decades. Hopes of finding survivors faded as rescuers pulled back fearing another explosion after at least 25 miners were killed. The accident, the worst U.S. 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.

“At this moment, there are still people missing, There are rescue teams that are searching tirelessly and courageously to find them,” Obama said at an Easter prayer breakfast in the White House.

“Rescue teams have been called back because of the amount of methane in the mine,” West Virginia mining spokesman Hoy Murphy told AFP.

“Crews are working to drill bore holes into the side of the mine to release the methane that’s built up in the mine shaft until it is safe for them to go back in.”

West Virginia Governor Joe Manchin said it would take at least 12 hours to drill the holes, so crucial time will pass before rescuers can get back into the mine.

“This is a tough one,” he said. “The families have talked about it. If there’s a shred of hope, it’s a hope for a miracle.”

Authorities were clinging to hope that the workers could have reached a rescue chamber where there is 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.

“And I will demand answers,” Rockefeller said in a statement. “We will leave no stone unturned in determining how this happened and in taking action for the future.”

The facility is run by Performance Coal Company, a subsidiary of Massey Energy, the fourth biggest coal producer in the U.S. which operates some 50 mines across the country.

“We in West Virginia revere our coal miners,” said Rockefeller. “We know their unique sacrifice, and we are forever in their debt.”