A balcony crowded with dozens of people at a popular bar and casino collapsed, injuring at least 70 people, officials said Saturday.

There were no immediate reports of any deaths from the accident Friday night at the Diamond Horseshoe Casino (search).

Polson (search) Fire Chief Tom Maloney said seven of the injuries were serious or critical, but the others did not appear to be life-threatening. It was not immediately clear what caused the 14-foot-high balcony to collapse.

"Most of the victims appear to be young folks enjoying a night out," Maloney said.

Investigators returned to the scene on Saturday to inspect the rubble of the wooden structure. No one answered the phone at the Diamond Horseshoe on Saturday.

An official at Polson's St. Joseph Hospital (search) said 54 people were treated there for injuries sustained in the collapse, but declined to release any details on the extent of injuries.

Emergency crews responding to a call found a "chaotic scene," Maloney said.

"There were injured people all over the ground, a lot of people wanting immediate help," he said.

One witness told radio station KERR in Polson that he heard two loud snaps or cracks just moments before the collapse.

Maloney said the balcony passed its most recent inspection, conducted as part of a routine fire inspection. It was not immediately clear when that occurred.

Witnesses estimated that between 100 to 150 people were on the 14-by-56-foot deck.

A Polson attorney representing the Diamond Horseshoe, Matt O'Neill, said he was told by club personnel that 50 to 60 people were on the deck.

O'Neill said a board attaching the balcony to the wall of the building gave way. However, he said the deck "met or exceeded all codes" and had been inspected twice in the past five years.

He said it appears some of the wood on the supporting board "rotted and gave way."

More than 30 people with the most serious injuries were taken to the local hospital by a dozen ambulances, many of them brought in from neighboring communities. People with less serious injuries were transported in private vehicles.

Maloney said the bar and casino overlooking Flathead Lake is a popular night spot in Polson, made even more popular this weekend because of a three-man basketball tournament in town.