ROCKLAND — A Rockland firefighter who experienced shortness of breath while battling a house fire Sunday is expected to be released from the hospital Tuesday.

Carl Anderson, a six-year veteran of the Rockland department, was taken initially to Pen Bay Medical Center in Rockport and then flown by LifeFlight helicopter to Maine Medical Center in Portland.

Anderson was on the second floor of the 384 Old County Road house running a hose when he became ill.

He left the building without assistance, but was transported to Pen Bay Medical Center for evaluation, Rockland Fire Chief Christopher Whytock said Monday in a news release.

“Due to the possibility that he’d inhaled countless unknown toxic gases within the smoke, he was shipped to Maine Medical Center for overnight observation. We expect firefighter Anderson will be released from Maine Med tomorrow morning with a clean bill of health. The circumstances of this incident are being investigated to ensure that all of firefighter Anderson’s equipment worked properly,” the chief said.

The fire was reported shortly before 3:30 p.m. Sunday. The property is owned by Douglass Conway Jr., according to city assessment records.

Heavy smoke and fire were found at the top of the stairway when crews entered the home. When the bulk of the fire was knocked down, it was still smoldering within the walls, Whytock said.

Other crews opened up the walls to locate any hidden fire that wasn’t accessible to the initial attack, he said. The building also had to be vented to release the heated smoke and toxic gases given off during the fire, by removing two windows on the second floor.

The second floor had moderate fire and smoke damage, while the first floor had smoke and some water damage.

Because of the damage from the fire, as well as the injury of the firefighter, the State Fire Marshal’s Office was called to help determine the cause of the fire, Whytock said.