TROY, N.Y. -- Fire officials are investigating what caused an overnight fire at a vacant home in Troy.

Authorities say the call for the fire came in just after midnight for the Second Avenue home. Spectrum News is told the home was purchased by a private buyer about three months ago and no one was living on the property.

This is the fourth fire in the last two weeks in Lansingburgh and Troy, including fires last week on Park Avenue and 5th Avenue, plus a fire that spread to a grocery store at 5th Avenue and 125th Street on July 5.

Fire Chief Tom Garrett says all four fires are considered suspicious. The July 5 fire is being investigated as arson.

According to Mayor Patrick Madden’s office, there are about 570 vacant properties in Troy. The city owns only 54 of them.

“Crews are out inspecting all the time and looking for vacant buildings, looking for structural problems, and that's our job and we'll continue to do that,” says Garrett.

Madden says the best thing to do is remain vigilant and report any suspicious activity you may see. Officials say it is too early to determine if all four fires are connected.