Gorham High School was evacuated Monday after a bomb threat was found inside, but police found no evidence of a bomb after a sweep of the building, authorities said.

Police were notified of the threat about 11:40 a.m., and the decision to evacuate the school was made after officers met with the administration, according to Deputy Chief Christopher Sanborn.

“Bomb detection dogs were called to assist with the search of the high school,” he said in a news release. But they didn’t find anything, and students and staff were later allowed to return, he added.

Sanborn said the incident is being investigated by police with assistance from the school administration.

In an email statement, Superintendent of Schools Heather Perry did not specify what form the threat took or how it came to the attention of the school district.

“I can’t give details to this as it is now an ongoing investigation,” she said.

Perry said parents and guardians were notified of the incident.

A bomb threat on Feb. 28 also forced the evacuation of Gorham High. Dogs from the Maine State Police were sent to the school and no bomb was found. Students returned to class the next day.