Harvard Police are investigating three reports of vandalism that occurred last Monday night or early last Tuesday morning at the Bromfield School and in the center of town. The damage will cost $2,500 to $3,000 to repair, police estimate.

At 5:30 a.m. on Tuesday, Oct. 11, a teacher at the Bromfield School, 14 Massachusetts Ave., told police the granite sign in front of the school had been knocked over, according to a police report. In the course of investigating the incident, police say, they discovered that the sandwich boards on the town common had been taken down and stacked.

Although it costs about $100 to upright the granite Bromfield sign, this is the second time in three months the sign has been pushed over. If the sign cracks, police say, it could cost $5,000 to fix.

At 8:11 a.m., also Tuesday morning, a janitor from the Bromfield School reported further vandalism. According to police, a person or a group of people had climbed onto the roof of the school using a ladder they then left behind. Once on the roof, the vandals pushed a safety rail over the wall, police say. The janitor told police it would take three or four men to lift the railing, police report.

The rail will have to be lifted back onto the roof by crane, police say, at a cost of $2,000.

Also during that incident, police report, the vandals gained entry into the school and broke into an IT room using a crowbar, breaking a door that will cost $500 to repair. The vandals rummaged through the room, but didn't steal anything, passing over laptops and other valuable equipment, police say.

The vandals did remove a personal item from a teacher's desk and left it in the high school field and took two fluorescent light bulbs that had been stacked against the wall and smashed them outside, police say.

A third incident wasn't reported until 11:41 a.m. on Wednesday, Oct. 12, but police suspect it occurred at the same time as the vandalism at the school. A mailbox in front of the Harvard General Store on Still River Road had been taken off its post and stuffed inside the U.S. Postal Service box there.

Harvard Police have not made any arrests in these cases, but they say they hope to use security camera footage from the General Store to identify some suspects. Because of the weight of the rail pushed off the high school roof, police say they suspect the vandalism was caused by a group of people.