New London — A leak that led to a fire has displaced two families from the troubled — and soon to be vacant — Thames River Apartment complex on Crystal Avenue.

City firefighters responded Saturday evening to a fire alarm activation and found the first floor of Building B filled with thick black smoke, Battalion Chief Tom Curcio said.

The smoke had reached multiple floors and firefighters evacuated four people who were still on the ninth floor.

Curcio said the cause of the fire appeared to be a water leak from a hot water pipe in a seventh-floor unit. Water had flooded the unoccupied unit and leaked down to the first floor. The actual fire started at the fire alarm panel.

There were two families and seven people living in the building, where power is now shut off. Firefighters continued late Saturday to secure the leaking pipe.

The Red Cross was on scene and as of late Saturday was aiding three people, a mother and two kids, with accommodations for the night.

There are 10 families still living at the apartment complex, with at least half with leases and preparations underway to move. The federally subsidized complex is managed by the New London Housing Authority but is being vacated because of deteriorating conditions. All of the families have received Section 8 vouchers and either moved or are in the process of moving.

g.smith@theday.com