GRAND ISLAND, Neb. (AP) — State investigators say homemade explosives caused the fire in which a Grand Island business owner died.

The Nebraska fire marshal’s office said in a news release Tuesday that “this incident was the result of manufacturing of homemade explosives by the deceased.” The release says no other information about the blasts is yet available.

Authorities say 65-year-old Mike Winfrey’s body was found early Monday morning inside the building that housed his Winfrey Plumbing and Heating operation. His father, Doyle Winfrey, owned the structure, which the office says is probably a total loss.

Firetrucks were dispatched after several people reported hearing explosions around 10:45 p.m. Sunday. An estimated 40 firefighters battled the flames. Two injured people were treated at a Grand Island hospital and released. Their names haven’t been released.