Norwich — Police and fire officials have activitated an arson task force to investigate the July 3 fire that damaged a historical former Ponemah Mill boarding house at 3-7 S. Second Ave.

Fire Marshal Kenneth Scandariato said Friday the three-alarm fire started in the basement below a former convenience store space and was incendiary in nature. The fire progressed up the side walls into the flooring and damaged all three floors in the 1895 building, Scandariato said. One family who lived in the opposite end of the building was displaced.

“It's still under investigation,” Scandariato said. “We're interviewing people. We're actively investigating and we got the task force in motion.”

He declined to comment further on how the fire was started or any possible suspects.

Signs have been posted offering a possible reward of $2,500 for information leading to an arrest and conviction in the case. Anyone with information is asked to call the state arson tip line at 1-800-84ARSON, (800) 842-7766. Norwich Fire Marshal Mark Gilot is in charge of the fire investigation and is working with Norwich police detectives.

The fire proved difficult to fight and went to three alarms and took several hours to extinguish. Crews from eight volunteer fire departments and the city's paid fire department responded.