Rescuers on Thursday were forced to pull out of a U.S. coal mine, halting efforts to search for 4 miners unaccounted for after an explosion left at least 25 dead.

West Virginia governor Joe Manchin (R) and Kevin Stricklin of the U.S. Mine and Safety Administration deliver news at a press conference near the Upper Big Branch Mine in Montcoal, West Virginia, April 8, 2010. [Xinhua/AFP Photo]

Kevin Stricklin, an official with the Federal Mine Health and Safety Administration, said the they were forced to abandon the rescue at the Upper Big Branch Mine in West Virginia because of dangerous gases, which could explode and put the rescue crew in danger.

The rescuers were digging their way to underground refuge chambers, where they hope to find the four missing miners. The airtight chambers were stocked with water, food and oxygen supply. Rescuers were within 300 meters to reach the chambers.

"This was a scenario that we didn't want," West Virginia Governor Joe Manchin said.

The blast occurred Monday at the mine operated by a Massey Energy subsidiary, nearly 50 km south of West Virginia's capital Charleston. It left at least 25 miners dead and 4 unaccounted for. Rescue workers were working day and night to reach the possible survivors since then.