SAN FRANCISCO -- Three people were killed and nine injured after an under-construction hangar collapsed at the Boise Airport in Bosie, capital of Idaho, on Wednesday.

The three died at the scene, and five of the nine injured are in critical condition, said the Boise Fire Department.

The hangar, located on the airport property, was owned by private charter flight company Jackson Jet Center, said Jackson Jet Center spokesperson Jessica Flynn, there were "dozens of dedicated people" working at the site at the time.

"We do not know exactly what caused the hangar collapse. Our focus now is on supporting our team and partners during this difficult time," Flynn said in an email to local media.

Calling the incident "catastrophic," Aaron Hummel, operations chief for the Boise Police Department, said the department is heading the investigation.

The operation of the airport are not being affected, according to officials.