CRESTED BUTTE, Colo., March 6— An explosion destroyed a two-story bank in the downtown section of this western Colorado ski resort this morning, killing three people and injuring 14, three of them critically.
The cause of the explosion, which leveled everything but the vault at the Crested Butte National Bank, was unknown. But the authorities said they were investigating the possibility that a buildup of methane gas or a bomb caused the explosion.
Two restaurants in the town received bomb threats in the last week and one was evacuated, said Chief Hank Smith of the Crested Butte police.
Rescue efforts were hampered by heavy snow that fell on this mountain town of about 1,000 people 250 miles west of Denver. But Mayor Wes Light said the authorities appeared to have accounted for all the people believed to have been inside the building when the explosion occurred at 9:15 A.M., shortly after the bank opened.
As firefighters and volunteers dug through the rubble by hand to rescue survivors, the Federal Bureau of Alcohol, Tobacco and Firearms sent a 12-member investigation team to Crested Butte.
It was not immediately clear whether there might have been an attempt to rob the bank.
About 200 people quickly came to the scene and started digging with their hands.
''They started digging through the rubble, helping the people who were still alive,'' said Mark Reaman, a photographer for The Chronicle and Pilot newspaper.
Hope Ostheimer, who works nearby, said the building ''completely collapsed on itself.''
''People started running from their cars and businesses and just started digging,'' said a passer-by who identified himself only as Brad.
''I started digging, but I wigged out when I saw the condition of one of the victims,'' he said. ''One guy crawled out,'' he said, but the rest were trapped.
Six of the injured were taken to Gunnison County Hospital 30 miles away, and the others were treated at clinics, Mayor Light said.
Tom Yates, chief of the Gunnison Police Department, said three people were in critical condition.
Three people were killed when a bank in Crested Butte, Colo., was destroyed by an explosion yesterday. Rescue workers searched through the rubble of the two-story building, which was almost levelled.