A neighbouring business owner said it sounded like "10 shotguns going off at once. Everything shook." He immediately dialled 111 and did his best to provide comfort while waiting for emergency services to arrive.
Two ambulance from St Johns in Levin were quickly at the scene. The injured man was flown by helicopter to Wellington Hospital in a serious condition.
Investigations to the cause of the fire were underway.
Fire and Emergency staff from Levin examine the exploded drum.
