Three people were killed and nine others were injured when a privately owned hangar under construction collapsed on airport property in Idaho’s capital Boise on Wednesday evening, city officials said.

Officials have identified the three victims as Craig Durrant, 59, of Boise, Mario Sontay Tzi, 32, and Mariano Coc Och, 24, of Nampa, Idaho. The bodies of the men were found underneath the rubble of the collapsed hanger.

Of the nine injured survivors, five were in critical condition and receiving care at hospitals on Wednesday night, city officials said.

The city’s fire department said the metal structure collapsed around 5 p.m. on Wednesday.

“This was an incredibly large emergency response involving many agencies from around our community,” said Boise Fire Division Chief of Operations Aaron Hummel, calling the collapse “large-scale” and “catastrophic.”

The building under construction was not a city facility and airport operations were not affected, Hummel added.

City officials said the area has been secured with fencing and the cause of the collapse is being investigated by the federal Occupational Safety and Health Administration.

Boise Mayor Lauren McLean thanked first responders and emergency response teams for their quick response and said, “the community is facing a profound loss.”

“(The collapse) occurred just west of our existing Jackson Jet Center at our new 39,000-square-foot steel hangar under construction, where dozens of dedicated people were working on site,” Jackson Jet Center, which owns the structure, said in a statement reported by CNN affiliate KIVI-TV.

“We do not know exactly what caused the hangar collapse. Our focus now is on supporting our team and partners during this difficult time.”

Jackson Jet Center offers private airplane charters throughout the US and Canada, with private hangar space and pilot service facilities located at Boise and Phoenix airports, according to its website.