KITTERY – Police interrupted four people – including one from Massachusetts – allegedly trying to steal a brass boiler weighing roughly a ton from a boarded-up former nursing home.

Responding to a report of suspicious activity, police arrived at the unoccupied Homestead Nursing Home on U.S. Route 1 on Monday night. They spotted two people running from a large opening in the back of the building and two others in a parked pickup truck.

Police said the boiler had been moved to an opening in the building. A chain was attached to the boiler and several tow straps lay on the ground near the front of the truck.

“We estimate that the boiler weighed approximately 1 ton and had a street value of over $3,000,” Lt. Russell French said. He said it was 41 inches wide, more than 95 inches long and had 3/4-inch-thick brass.

The opening in the building, which hasn’t been occupied for years, had been made by removing a door and several window louvers from the basement’s boiler room.

The four suspects, all charged with burglary, were identified as Justin Knowles, 29, and Eric Graham, 22, both of Seabrook, N.H.; Jason Lamos, 31, of Epping, N.H.; and Kathleen Theresa Fleming, 20, of Lowell, Mass.

They were taken to York County Jail, where they were being held on $1,000 bail.

Metal thefts have been a growing problem in the region, driven by a 400 percent rise in the price of industrial metal over the past five years.