RAYTOWN, Mo. — Federal investigators believe a man illegally making fireworks in his basement caused an explosion that leveled part of a suburban Kansas City duplex, killing him and injuring at least three others.

Investigators with the Bureau of Alcohol, Tobacco, Firearms and Explosives came to that conclusion after sifting through the rubble Tuesday at the explosion site in Raytown, ATF spokesman John Ham told the Kansas City Star.

Officials found the body of the man in the basement of the duplex hours after the explosion and fire Monday night. Authorities have not released his name.

Officials said five people — including two children — were in the building at the time of the explosion. One child was treated for injuries at a hospital and one adult underwent surgery for injuries on Tuesday.