A massive underground explosion has killed 25 coal miners in the U.S. state of West Virginia. Rescuers are searching for four other miners who are missing.
Monday's explosion was the worst mining disaster in the United States in more than two decades. It is blamed on methane gas that accumulated in underground chambers and ignited.
West Virginia Governor Joe Manchin says the sheer devastation caused by the blast is dimming hopes the four missing miners will be found alive.
"We hope for a miracle here, but the odds are long against us," Manchin said. "We know it was a horrendous explosion because of what it did to the railroad tracks [in the mines]. It twisted them like pretzels. That is a tremendous force."
The governor was speaking on NBC's Today show.
Continued build-up of dangerous gases have hampered rescue efforts. If the four miners survived the blast, they would attempt to make use of "refuge chambers" with air tanks located inside the mine, according to Kevin Stricklin of the U.S. Mine Safety and Health Administration.
"It is a rescue operation," Stricklin said. "It is definitely not a recovery operation. The refuge chambers have the ability to provide 96 hours of oxygen. So we have time on our side."
At the White House, President Barack Obama pledged the full efforts of the federal government in support of rescue efforts, and expressed condolences to the families of workers who died in the blast.
Located south of West Virginia's state capital, Charleston, the mine is operated by Massey Energy Company, which has been fined repeatedly for safety violations, including failures to properly ventilate mines of combustible gases.
"I would call this [accident] an anomaly, but we better find out what happened so that it does not happen again," said former miner and author Homer Hickham. "I am still shocked by this, not that there was a methane explosion, but that it had so much energy behind it, which indicates a rather large build-up [of gas] over time."
The West Virginia incident follows last month's flooding of a Chinese mine that left more than 100 workers trapped for more than a week.
Hickham says that, compared to China, where thousands of miners perish each year, U.S. mining operations are relatively safe.
"The American mining industry is the safest in the world," Hickham said. "We have a highly-regulated industry, while the Chinese, essentially, have no regulation and practice very unsafe techniques."
Years ago, Beijing acted to improve safety standards at Chinese mines, including stricter evaluations of government inspectors and greater compensation for workers who are injured or killed.
U.S. officials have pledged a thorough investigation of the West Virginia disaster.