Candlelight memorial service at Sago Baptist church

U.S. officials are investigating the West Virginia coal mine accident that killed 12 workers and left a 13th miner hospitalized in critical condition.

The mine was cited last year for more than 200 violations of federal safety regulations - several of them involving conditions that could lead to an explosion.

Officials also are trying to learn why initial reports wrongly said 12 miners had survived. The reports spread quickly to relatives of the trapped miners. Those relatives now want to know why they were given false information when only one miner survived the accident.

Doctors say the one survivor - 27-year-old Randal McCloy - remains in a coma after being exposed to carbon monoxide while trapped with his co-workers. They say he suffered damage to his heart, kidneys and lungs.

The explosion early Monday was the worst U.S. mining disaster since 2001, when a blast in Alabama killed 13 people.