FARMINGTON, Maine (AP) Federal and state investigators are working to pinpoint the source of a propane explosion that leveled a building and killed a firefighter in Maine.

Investigators from the State Fire Marshal’s Office and the Bureau of Alcohol, Tobacco, Firearms and Explosives are starting to process the scene Tuesday in Farmington.

The explosion on Monday shattered the two-story building that housed LEAP Inc., a nonprofit that serves people with cognitive and intellectual disabilities. The blast killed 68-year-old Fire Capt. Michael Bell and injured his brother, Fire Chief Terry Bell; five other firefighters; a maintenance worker for LEAP; and an ambulance worker.

The blast also destroyed homes in a nearby mobile home park. The Red Cross is helping 10 people who were displaced with food, housing and other essentials.