Norwich – Firefighters battled a fire at the vacant YMCA building on Main Street Monday, the second arson fire in as many nights in vacant downtown buildings and the third in the past week, Fire Chief Kenneth Scandariato said.

The YMCA fire started at 6:20 p.m. in the rear of the second story that once housed  boarding rooms. Scandariato said there were signs of forced entry and said he has asked city building officials to “seal the building up tight.”

“Whoever started the fire came in through the back,” Scandariato said. “It was incendiary.”

Scandariato said a fire Sunday afternoon at the giant vacant mill at 132 Franklin St. also was set. Days earlier, a mattress was set on fire up against a building on East Main Street. He said it's too soon to tell whether the fires are related.

Scandariato, who also serves as city fire marshal, said his office and city police are investigating all three fires.

Firefighters from the Norwich city department and the Laurel Hill and East Great Plain volunteer departments fought the YMCA fire, which took about 45 minutes to be brought under control. Scandariato praised responding crews, saying the fast arrival and tactics prevented the fire from spreading under dangerous, dark, smoky conditions. Burning furniture and plastic contributed to the “blackout,” the chief said.

The abandoned building has no electricity. Ladder truck crews fought the fire through the roof, while other firefighters entered through the front doors on Main Street to reach the second floor. They had to search for the fire in thick black smoke, Scandariato said.

The fire damage was contained to one room, while smoke and water damage occurred to surrounding areas.

One firefighter received a minor laceration injury, was treated at the scene and returned to work, Scandariato said.

On Sunday afternoon, the fire department was called to the Franklin Street mill when someone spotted smoke, and firefighters had to enter the massive 216,000-square-foot building to find the fire and quickly extinguish it.

c.bessette@theday.com