The three-alarm fire at the former Quincy, Massachusetts, City Hall early Tuesday morning was started by people attempting to remove copper pipes from the building, the State Fire Marshal's office says.
The call for the fire came in shortly before 1 a.m. No mutual aid was provided. The fire started towards the rear of the building.
The building, which is right next to the new city hall, is a building undergoing a restoration project.
The fire chief said though the building is under construction, it is structurally sound and the roof is completely intact. There is substantial damage to the building however, and officials say it is a setback for the restoration project.
Mayor Thomas Koch said that the damage will be covered by the insurance that the contractor carries.
There was no damage to the new city hall and it will be fully functional Tuesday.
There were no injuries to any firefighters or first responders.
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The incident remains under investigation.