An unspecified written threat on a bathroom wall and a mechanical error sounded the alarm twice at Attleboro High School Wednesday morning, forcing students and faculty to evacuate two times in the same hour.

The first alarm sounded shortly after 9 a.m. The second one went off at 9:43 a.m. Both alarms interrupted an assembly attended by juniors and seniors featuring former Boston Celtic Chris Herren, who spoke about his drug addiction and recovery.

Attleboro Detective Sgt. Arthur Brillon declined to specify what the handwritten threat stated, but he said "school officials took the appropriate action" to notify the police. There is an active investigation and "some evidence" was obtained at the scene by detectives Alex Aponte and Todd Boldy, he said. The detectives will review a videotape provided by the high school.

AHS principal Bill Runey wrote in an email to Attleboro Patch, "The two evacuations were completely unrelated. The first was an issue at a fire box adjacent to the auditorium. The second was the appropriate response to a message in a bathroom."