About 200 people attending adult education courses in Montreal on Monday evening were locked in their classrooms for more than two hours.
The alert sounded around 9 p.m. at the Yves Theriault Centre on Villeray St. near 21st Ave.
"We were in class and we heard the code orange through the speaker," said one man. "We have rules to follow: we close all the doors, we shut down all the windows, and then we put all the bags on the door."
Police rushed to the school and then spent two hours going classroom to classroom in search of a threat.
"They searched all the rooms, and they didn't find anything," said student Kiro Bob.
He said some students were nervous while police were searching the building.
"Some of them were scared, but it was all okay," he said.
Police eventually checked every room and found no sign of any threat.
They believe something went wrong with an automated alert system.
