Groton — A passerby broke down the door and neighbors helped him rescue a woman from a fire that left a multi-unit residence on Thames Street uninhabitable on Thursday evening.

City of Groton Fire Chief Robert Tompkins said firefighters received a call about 4:30 p.m. to check on a possible fire in the structure's basement. When firefighters arrived, they saw heavy smoke, and it quickly went to a first-alarm fire and ultimately a third-alarm fire, tripling the amount of personnel and resources called to the scene.

The fire extensively damaged the double duplex with four units at 273-279 Thames St., and it is uninhabitable, Tompkins said.

American Red Cross was on scene to assist residents. The agency said late Thursday that three families — six adults — were displaced by the fire.

Groton Ambulance transported two women who lived there to be treated for smoke inhalation, Tompkins said. City police Officer Reggie Stanford administered oxygen to a cat that a firefighter rescued.

Firetrucks lined the street and firefighters in ladder trucks battled the blaze, as a group of neighbors gathered to watch and take videos.

Eric McElroy, who lives nearby in the neighborhood, said his 23-year-old daughter, Molly, smelled smoke from her second-floor room. Anytime they smell smoke, they check because the neighborhood has experienced several fires.

"After three fires in this neighborhood already, you kind of get paranoid," Molly McElroy said. 

They determined it was coming from 273-279 Thames St. after they saw smoke around the chimney and a haze in front of the building, they said. Then, they saw smoke coming from the basement.

Eric McElroy said he ran back to grab his phone and called 911. He said a man driving by pulled up and asked if anybody was inside, and he responded that he hadn't had time to check because he was calling 911.

Eric McElroy said the man then kicked down the door and went inside to help an elderly woman. The man, along with Eric McElroy and a couple that had been walking by, helped carry her out of the building. They also helped make sure another woman got out.

The man, who was wearing a blue T-shirt, left the scene and his name was not immediately available.

Glenn Gray said he noticed smoke from his residence up the hill and came down to Thames Street, where he saw black smoke coming out of the windows of the building.

Tompkins said at 6:40 p.m. that the bulk of the fire was extinguished but because the building is old and has void spaces in the walls, firefighters were continuing to work extensively to make sure the fire was completely out.

The cause of the fire is under investigation, but the initial report is that plumbing work was being done in the basement at the back of the building, he said.

The response included fire departments from the City of Groton, Poquonnock Bridge, Old Mystic, Mystic, the submarine base, Gales Ferry, Ledyard, Montville, Mohegan Tribe and Electric Boat, as well as the City of Groton Police, Groton Ambulance and Waterford Ambulance, Tompkins said.

k.drelich@theday.com