SEARSPORT – A lobster fisherman was listed in serious condition Friday afternoon at Maine Medical Center in Portland after an explosion threw him from his boat Thursday night.

Kenneth Grant Jr., 37, of Searsport was working on the engine of the 23-foot-long lobster boat at about 8:30 p.m. when the explosion occurred, according to Sgt. Sam Payson of the Searsport Police Department. The boat was tied to the town wharf at the time, he said.

Witnesses were not sure whether the engine was running at the time of the explosion, or if Grant was trying to get it started, Payson said.

One person told Payson he thought he heard the engine backfire, which may have caused gas fumes in the engine compartment to ignite.

“We’re not quite sure what happened,” Payson said.

The force of the explosion threw Grant from the boat, police believe.

Officer Mark Pooler was patrolling in the area and was on the scene shortly after the explosion, followed by the Fire Department and ambulance, Payson said. Grant was conscious and in the water, where he was told to remain until emergency medical technicians could begin to treat him.

Payson said he believes Grant suffered second-degree burns from the accident. He said the fisherman was taken by ambulance to Waldo County General Hospital in Belfast and then transferred to a burn treatment unit at Maine Medical. The boat was deemed a total loss.