A fire at a vacant house on South Irvine Avenue Monday night was the 30th blaze in Sharon that was intentionally set in the last few years.

Firefighters were called at 9:39 p.m. to 671 S. Irvine, Chief Terry Whalen said.

A neighbor at the duplex next door called 911 after she smelled smoke.

“The greatest resource is neighbors keeping an eye on their neighborhood,” Whalen said.

Many in the area came outside to see what was going on when fire trucks and police cars blocked off the road between Davis Street and U.S. Route 62 and Emmanuel Place.

“We were just sitting there watching TV and heard sirens,” said neighbor Joe Kinsey.

Kinsey’s fiancee Lorie Norris said she’d seen people go in and out of the house recently and figured it was homeless people trying to find somewhere to stay.

“It’s sad,” she said, adding that some used to sleep under the Route 62 bridge, which runs over the railroad tracks parallel to Irvine.

Now that the bridge is under construction and it’s getting colder, those folks are looking for warm places to stay, Ms. Norris said.

Police confirmed that homeless have been known to sleep under the bridge but said that the opening of the men’s shelter Joshua’s Haven in downtown Sharon has been very helpful.

Even if a structure is supposed to be vacant, the fire chief said they have to go in as if someone’s inside.

“That’s always our greatest fear — that someone’s in there,” Whalen said.

Smoke filled the air as firefighters knocked down the fire at the triplex, which started in the northeast corner of the building, Whalen said.

There are no utilities serving the house and the fire started near the upper rear east side door and extended into the attic, Whalen said. Fighting the blaze became problematic because only one apartment in the building has access to the attic.

“It’s a huge house,” Whalen said, adding that by the time firefighters found the flames in the attic it had burned through the roof.