Rockland Fire Chief Scott Duffey is credited with saving a helpless dog tied to a work bench in a burning apartment on Monroe Street Monday.

Fire officials say it appears a lit cigarette sparked Monday’s fire in a third-floor apartment at 85 Monroe St., where the terrified boxer clung to life by hunkering down on the floor.

“I went upstairs to search for victims. That’s when I saw the dog tied up,” Duffey said.

Fortunately, the dog was lying flat on its stomach. This provided a pocket of air in the smoke-filled room for the dog to breathe and stay alive, Duffey said.

Duffey untied the 40-pound dog and carried it to safety.

The apartment was unoccupied when the building owner reported the fire at 1:50 p.m. Monday, Abington Fire Chief John Nuttall said.

It took firefighters from Abington, Whitman and Rockland about 15 minutes to knock down the fire, which traveled up a rear wall and threatened to spread into the attic.

The state fire marshal’s office investigated. Weymouth firefighters manned the Abington fire station.

“It appears at this point (the fire) was due to improper disposal of smoking materials,” Nuttall said.

The apartment’s smoke detectors also did not work. This caused a delay in the fire’s detection, he said.

Nuttall said firefighters tore down the rear wall to make sure the fire was out.

“This is a large, old house. My main concern was the fire was going up into the attic,” Nuttall said.

The chief said that smoke and fire, and water to douse the fire, caused an estimated $20,000 in property damage.

The second- and third-floor units were not habitable as of Monday, he said.