Two firefighters sustained severe injuries in an explosion at a fireworks storage facility south of Roswell, New Mexico, on Wednesday.

About 12 firefighters were packaging fireworks in the storage area for an upcoming Fourth of July display when the explosion occurred around 12:15 p.m local time, according to the New Mexico State Police.

Two of the firefighters were air-lifted to a trauma center for life threatening injuries and the other ten were treated for minor injuries at the scene.

Authorities have not said what caused the explosion.

New Mexico State Police and the Bureau of Alcohol, Tobacco, Firearms and Explosives are taking lead roles in the investigation. Roswell Fire Department, Roswell Police Department, and the FBI are assisting.