NEW HAVEN, Conn. — Connecticut authorities are treating the Christmas Day fire that heavily damaged the historic home of Walter Camp — a Yale graduate credited with developing American football — as suspicious.

New Haven Fire Chief John Alston said officials are considering the blaze suspicious because the three-story, wood frame Victorian structure was vacant, secured and without power at the time.

He said the cause of the fire is still being investigated.

Fire officials have said no one was inside the structure at the time and that the third floor collapsed in the blaze.

The house, built in 1900, had been recently purchased and was under renovation.

The New Haven Register reports the 11,340 square foot building previously served as the home to the AIDS Interfaith Network, which sold it in 2015.

The building was most recently sold in November for $1.2 million to 1303 Chapel NH LLC, the newspaper reported.

Camp, who was born in New Britain, Connecticut, is considered the father of American football.

As captain of Yale's rugby team, he tweaked the rules of the English game, introducing concepts such as the line of scrimmage and the quarterback position.

He also established American football's system of downs and points, the number of players per side, tackling below the waist and other now familiar rules.

And Camp helped create what is today the National Collegiate Athletic Association, or the NCAA, which governs college sports. He died in 1925.

New Haven firefighters also battled a Christmas morning blaze at a waste recycling plant.

They say that fire appears to be accidental and that people who were in the building at the time escaped safely.