A 44-year-old man was burned over a quarter of his body in Waianae Tuesday afternoon.

The city Emergency Medical Services Division reported the man was in serious condition with first-degree burns at Apana Road when he was taken to a hospital.

The injury was reported at 12:48 p.m.

Fire Capt. Tyler Chan said the man was at a neighbor’s former pig farm using an arc cutter — a torchlike tool — to cut something.

Chan said firefighters initially suspected he may have been burned by a flash from a flammable gas since there was no sign of an extensive fire.

A hazardous materials unit was dispatched to search for a leak of flammable gas, but no trace was found, he said.

The cause remains undetermined, Chan said.