BANGOR — For the second time in three months, a faulty heating unit is being blamed for a carbon monoxide leak at a Bangor beauty school.

Empire Beauty School said its building was evacuated this morning after a strong odor was noticed in a classroom and a carbon monoxide detector went off. The Bangor Daily News reports the school said more than a dozen students and two staff members were taken to area hospitals with nausea symptoms, and many were later released.

The school said technicians were called to repair the school’s heating unit. Classes were scheduled to resume Thursday.

In November, seven people at the school sought hospital treatment after feeling nauseated from a gas leak that was blamed on a malfunctioning heating unit.