Canton, MA – A natural gas explosion and fire officials say was triggered by falling ice has damaged a building housing offices of the Norfolk County District Attorney.

Fire officials in Canton said the fire broke out just before 2 a.m. Sunday in an outside gas meter line.

The fire mostly affected the exterior of the three-story brick building, where there was a partial wall collapse, but there also was heavy water damage to offices inside. The building has been declared structurally unsound.

District Attorney Michael Morrissey and staff members came to the scene after the alarm came in.

Morrissey’s second-floor office was most effected in a kitchen area where no vital work materials are stored, according to Morrissey. Damage is still being assessed.

A spokesman for Morrissey said they are looking for alternate locations for workers displaced from their offices, which are on the second floor of the building.

The state fire marshal’s office also is investigating.