The death toll of the coal mine explosion in West Virginia has risen to 25 early Tuesday, making the accident the deadliest mining disaster in the United States since 1984.
The blast occurred at the Upper Big Branch Mine, nearly 50 km south of the state's capital Charleston, at about 15:00 local time (19:00 GMT) on Monday when 29 miners were working inside the mine.
Kevin Stricklin, from U.S. Mine Safety and Health Administration, told reporters early on Tuesday that 25 bodies have been found and four others were still missing.
"The situation is dire," he said.
According to Stricklin, rescue teams have halted their efforts to search for missing miners due to the "high concentration of methane and carbon monoxide" in the mine.
Governor Joe Manchin, who met victims' relatives after the disaster, told reporters that seven bodies had been recovered and identified, but the other 18 have not been identified.
President Barack Obama extended his deepest condolences to those who lost loved ones, vowing that the federal government would offer assistance needed in the rescue effort.
"The federal Mine Safety and Health Administration will investigate this tragedy and take action," Secretary of Labor Hilda L. Solis said in a statement, adding that miners should never have to sacrifice their lives for their livelihood.
Massey Energy, the fourth largest coal producer in the United States according to revenues, operates 35 underground and 12 surface mines in West Virginia, Kentucky and Virginia, according to the company website.
The accident is the worst mine disaster in the country since a mine fire in Utah killed 27 people in 1984.
Mine deaths are relatively not common in the United States. Last year, the number of U.S. miners killed on the job was 34, 18 of them died in coal mines. Notable accidents in recent years include West Virginia's Sago Mine methane explosion, which killed 12 miners in 2006. Six also died in Utah's Crandall Canyon mine cave-in in 2007.