A fire started during some welding work on a cargo ship called the Mississagi at the Heddle Marina on Thursday afternoon. About 20 workers were on the ship, working on repairs over the winter.
Fire crews arrived after 3 p.m. to see heavy black smoke coming from the ship.
The workers had been welding and fire crews believe it ignited some combustibles on the job site, potentially flammable materials like paint, said Hamilton Fire spokesman Claudio Mostacci.
One of the workers was assessed for smoke inhalation but was not taken to the hospital. The fire department's confined spaces team had to be called in to ensure the fire was out inside the ship.
It was a busy afternoon for fire crews. They also spent hours on scene at Homestead Granite and Marble on the Mountain. The front portion of the business partially collapsed due to a fire that broke out around 1 p.m., and fire crews were still on scene at 5 p.m. Thursday.
The building will likely need to be entirely replaced and the extent of the damage at the granite store is about $330,000, Mostacci said.