UPDATE: Fire at Celtic Tavern Causes Extensive Damage

A fire originating from a mulch bed caused extensive damage to the Celtic Tavern in Northborough on Monday morning, Northborough Fire Chief David Durgin said.

A smoke alarm alerted Northborough firefighters at 6:45 a.m. Monday. When firefighters arrived, smoke was visible from the building and a working fire alarm was transmitted for additional help. Sounding a second alarm at 7:10 a.m., crews from Marlborough, Westborough, Shrewsbury and Southborough responded with mutual aid.

By 7:40 a.m., the fire was knocked down, but Durgin said it had caused significant damage "reaching or exceeding $50,000."

No injuries were reported.

The fire, which started in the mulch outside the building, climbed the wall facing Belmont Street and extended into the walls and up to the ceiling and roof area., Durgin said.

Through a joint investigation with the state fire marshal's office, the fire was ruled accidental, though how it began in the mulch is still being determined.

"We can't quite determine how the mulch ignited, but it's not suspicious," Durgin said.

The building will need some repairs, due to heavy smoke damage and structural damage to the walls and roof, he said.