DOVER – Police and firefighters determined a 9-year-old boy playing with a lighter started a three-alarm fire which severely damaged a multi-family apartment building Monday afternoon.

Police, firefighters and emergency personnel responded to 5 Western Ave. at 2:31 p.m. As the three apartment buildings, built in an “L shape” were connected by a single roof, firefighters sounded the alarms to bring more manpower to the scene, as the fire spread throughout the structure, according to assistant Fire Chief James Ormond.

“It was a hot day,” Ormond said. “There was a lot of fire.”

Ormond said the fire resulted in one minor injury — a resident who received minor scratches while attempting to encourage others to evacuate. He was treated at the scene.

Local firefighters were assisted by their counterparts from Durham, Newington, Pease Air National Guard, Portsmouth, Rochester, Rollinsford, Somersworth and South Berwick, Maine. Firefighters from Newmarket, Portsmouth, Berwick, Maine, and Eliot, Maine, provided station coverage.

While police and firefighters discovered the fire began after the boy was playing with a lighter in a breezeway, Ormond said investigators have not determined whether it was accidental.

“Given the age of the child who started the fire, he will not be subject to criminal proceedings, but will be diverted to alternate programming. No further identifying information regarding him will be released,” according to a joint release by police and firefighters.

“We’re still investigating it,” Ormond said, adding firefighters remind all area residents to be careful with fire, and he reinforced the message they often pass onto children: “Matches and lighters are tools, not toys,” Ormond said.

While four apartments were damaged by the fire, another eight sustained smoke or water damage, and Ormond said firefighters had to cut power to the building as a precaution. As a result, he said occupants of the 12 apartments were displaced.

Members of the American Red Cross responded to the scene to assist residents.