A possible gas leak forced the evacuation of nearly 800 students and teachers from Greely High School in Cumberland on Wednesday.
The odor was reported about noon, said principal Dan McKeone.
Students were moved to the adjacent Greely Middle School for about an hour while the building was ventilated.
When the Cumberland Fire Department cleared the building as free of gas, classes were nearly ready for dismissal about 1 p.m., McKeone said.
“It probably ate up most of the final period of the school day, about 45 minutes,” he said.
The Dead River Company, which supplies the school with gas, is investigating the cause of the odor, he said.