ROCKPORT — A worker at a Rockport metal fabrication business was killed Friday when a diesel fuel tank he was welding exploded.

Sean Rancourt, 39, sustained life-threatening injuries in the explosion at Rockport Steel shortly before 3 p.m., a Department of Public Safety spokesperson said in a written statement. Emergency responders treated him at the scene but he did not survive. His body was transported to the Medical Examiners Office in Augusta for an autopsy.

Rockport Fire Chief Jason Peasley said the cause of the explosion is under investigation. An investigator from the Office of State Fire Marshal arrived at the scene shortly before 5 p.m.

Emergency crews at Rockport Steel as officials investigate a fatal explosion Friday. Steve Betts/The Courier-Gazette

A customer had arrived and asked for work to be done on the fuel tank of a boat, Peasley said. Rancourt was working on the approximately 25-gallon tank when it exploded.

The building at 17 Rockville St., off Route 1, sustained minor damage, but shrapnel from the tank was scattered over a wide area.

Rockport fire and Rockport police were still at the scene after 5 p.m.

Rockport Steel specializes in custom metal fabrication projects including welding and cutting, according to the company’s website.