What brought down the Boise Airport hangar that killed three and sent five others to the hospital?

At 5pm on 31 January, a private, partially built hangar on the airfield of the Boise Airport crumbled under its own weight and collapsed into a heap of scrap.

Three people in the hangar were killed when it buckled and fell. Another nine were injured.

Emergency officials raced to the scene to assist the injured survivors. Five of the injured were rushed to the hospital in critical condition. As of Thursday afternoon, their conditions are unknown.

What brought down the hangar, and who were the victims?

The building collapsed around 5pm on Wednesday, 31 January.

Boise Fire Department Operations Chief Aaron Hummel said the building's metal framework failed, causing it to crash to the ground.

“There was a large-scale collapse of the building, the framework of the building,” Mr Hummel said, according to The New York Times. “It was fairly catastrophic.”

He described the scene as "chaotic," according to CBS News.

"I don't know what caused it, but I can tell you it was a pretty global collapse," he said.

A woman driving past the scene approximately a half-hour after the collapse said she saw the building's outer walls still standing, while the middle portion had collapsed between them.

The building was under construction at the Jackson Jet Centre at the time of the collapse, but it is not immediately clear if the nature of the work being done played any part in the structural failure.

A privately owned construction crane on the scene also collapsed, according to local officials.

Officials at the airport and law enforcement officials have not released the name of the hangar's owner as of Thursday afternoon. According to the city, there were no code violations connected to the construction project.

Three people died at the scene when the building came down on top of them.

Another five individuals required hospitalisation and were taken from the scene in critical condition. The conditions of the other four injured are not known, but they presumably had less-serious injuries than the five requiring hospitalisation.

The names of the victims have not been released.

Mr Hummel said that some of the victims were working on hoists or other elevated platforms at the time of the collapse, noting that some required specialised recuse efforts to remove them from the rubble.

“The Boise Airport, City of Boise, and all first responders extend their deepest sympathies to those impacted,” Mr Hummel said.

Approximately 30 people were working at the hangar at the time of the collapse. Boise firefighters worked to reunite workers with their families, and said all of the workers have been accounted for following the incident.

“Yesterday was a tragic day for our Boise community. Our heartfelt condolences go out to the families and loved ones affected by this incident,” Boise Fire Chief Mark Niemeyer said on Thursday. “I commend the actions of all the first responders for their quick and professional response rescuing victims and caring for patients in a chaotic and very dangerous environment.”

The city’s mayor also offered her condolences on Thursday.

“Our community is facing a profound loss after the hangar collapse last night. Our thoughts are with the families who lost loved ones and those who are awaiting news on those still in critical conditions,” Mayor Lauren McLean said. “We owe a debt of gratitude to our first responders and emergency response teams for their quick, compassionate and professional actions last night and into today and we hold everyone involved in our hearts.”

Red Sky, speaking on behalf of the Jackson Jet Centre, issued a statement to local broadcaster KTVB following the incident.

"Tonight, our hearts go out to everyone affected by this horrific event, especially those with loved ones on site when this tragedy occurred," the company said in the statement. "We're immensely grateful for the rapid and professional response of Boise Fire, Boise Police and Ada County Paramedics along with the expert care of our area hospitals."

The state's governor, Brad Little, asked the public for prayer for the victims and their families.

"Please keep the victims of the tragic building collapse near the Boise airport in your prayers. We are also praying for the loved ones of those who died. The State is monitoring the situation to find out how we can assist," he wrote on X/Twitter.

The Boise Fire Department led the investigation into the collapse on Wednesday, but turned the site over to OSHA officials on Thursday.

Mr Hummel noted that the structure that collapsed was a private building, and not a city building, but is still under the department's purview.

OHSA representatives will reportedly issue any further information regarding the collapse.

At the time of this report, it is unclear what exactly caused the building to crumble.

One of the lingering questions involves the crane on scene; officials are working to determine if the crane's collapse brought the building down, or if the building buckled and brought the crane with it when it toppled.

Investigators were on site Thursday trying to piece together exactly what happened at the hangar.