Three people died and nine more sustained injuries when a privately owned airplane hangar under construction collapsed in Boise, Idaho, Wednesday.

Five of those injured in the collapse, which occurred at 5 p.m. local time Wednesday, were in critical condition at nearby hospitals, according to a city press release. The collapse, which happened at the Boise Airport’s airfield, did not affect the airport.

Police said the collapse was due to a downed crane, according to local outlet KTVQ.

Meridian, Idaho-based Big D Builders was building the hangar, a spokesperson for the company told Construction Dive. The contractor declined to provide further comment.

City records show Big D Builders had obtained permits to build a 39,000-square-foot jet hangar for Jackson Jet Center, NPR reported. The $6.2 million project was to include the construction of a concrete foundation and a metal building. 

Fire crews worked to stabilize the collapse and rescue the injured. Boise Police, Gowen Field Fire Department and Ada County Paramedics also responded to the scene — totaling eight fire engines, three ladder trucks, two safety officers, two battalion chiefs, one division chief, a heavy rescue unit and a dozen ambulances, per the city’s release.

“There was a large-scale collapse of the building, the framework of the building. I don’t know what caused it, but I can tell you that it was a pretty global collapse that occurred,” Aaron Hummel, operations chief for the Boise Fire Department, said at a news conference Wednesday, according to CNN. “It was fairly catastrophic.”

OSHA officials have begun to investigate the collapse. The agency does not comment on ongoing investigations. 

The identities of the deceased and injured in the collapse were not released as of the time of publication.