New London — A two-alarm fire tore through a multifamily home at 26 Prospect St. on Friday, displacing 14 people and leaving one firefighter hospitalized with heat exhaustion.

New London firefighters arrived at 2:30 p.m. to find thick plumes of smoke billowing from upstairs windows of the 3½-story building. The residents had all exited the home and firefighters performed a search to ensure no one was left inside, fire Chief Thomas Curcio said.

The fire was extinguished, Curcio said, but not without an intensive amount of work by firefighters, who had to open up the walls to find hot spots where the fire had spread. Some older homes were constructed without firebreaks in the walls, allowing fire to move freely from floor to floor. Curcio credited firefighters with quick action that helped save the building.

One firefighter was taken by ambulance to Lawrence + Memorial Hospital for treatment of heat exhaustion. No other injuries were reported.

The building sustained extensive heat and water damage and Curcio said he did not expect occupants to return immediately. The Red Cross was on scene at 4 p.m. assessing the needs of the residents. Property records show there are at least five apartments in the building.

New London firefighters were joined at the scene by neighboring fire departments that included Waterford, Poquonnock Bridge in Groton and the Naval Submarine Base Fire Department.

The cause and origin of the fire is under investigation by the fire marshal’s office.

g.smith@theday.com