A hangar under construction on the grounds of the airport in Boise, Idaho, collapsed Wednesday, injuring about a dozen people, officials said.

Authorities responded at about 5 p.m., local time, to a private business located at the Boise Airport for a steel framed hangar that collapsed, Boise Fire Department Operations Chief Aaron Hummel said during a news briefing.

Everyone who had been at the site had been accounted for as of Wednesday evening, he said. Hummel wouldn’t comment on the condition of those injured or say whether anyone had died. He said officials were first working to contact family members.

“It was a very chaotic scene,” Hummel said, describing the incident as a “large-scale collapse” of the framework of the building.

“I don’t know what caused it, but I can tell you it was a pretty global collapse,” he said, calling it “catastrophic.”

Boise Airport operations were not impacted, officials said.

Terra Furman was driving on Interstate 84 about a quarter mile from the airport at about 5:30 p.m. when she spotted at least 20 police cars, ambulances and firetrucks around what she described as a crane folded in half and a building in the shape of an ‘M.’

“The walls were still up at a point and the middle collapsed in on either side,” she said.

Hummel said some of the victims were on a hoist or other elevated platform at the time the structure fell, and that required some specialized rescue efforts. He said a crane also collapsed in the incident.

Leticia Ramirez, a spokesperson for Saint Alphonsus Regional Medical Center in Boise, said emergency and trauma teams were working with first responders to treat patients who arrived from the scene.

Authorities are investigating what caused the collapse.