TOPSHAM — An unexplained gash might identify the person responsible for the worst vandalism spree in this southern Maine town in more than two decades, police said Monday.

Blood-splattered rocks were found where 28 plate glass windows were smashed at Mount Ararat High School. Blood was also found on some of the windows, said Topsham Detective Sonny Williams.

Williams said the vandal or vandals could possibly be identified by an unexplained gash from glass shards. Some of the windows apparently were broken by pounding on the glass with rocks, he said.

Damage was estimated at $20,000. A custodian discovered the vandalism early Friday.

School officials said it was the worst incident of its kind ever at the school, which has been damaged over the years by graffiti and broken windows.

The district had stopped funding a police officer who had been on duty at the school for several years, but is now considering bringing one back during school hours, said Williams.

“That’s the worst vandalism I’ve seen in town, and I’ve been here 26 years,” said Williams.

The damage happened the same night as the school prom, which was held in Portland, but police did not know whether there was a connection.

The detective encouraged anyone with information to contact him at the station.

“We’re hoping the public will help us,” Williams said.

Three custodians spent all day Friday sweeping up glass while workers from a glass company repaired some of the windows. All of the windows, some of which are 6 feet high, are expected to be repaired by the end of the week.

School was not in session on Friday due to teacher conferences. Mount Ararat serves the towns of Topsham, Harpswell, Bowdoin and Bowdoinham.