Norwich — The Norwich Stop & Shop Supermarket was closed for 2½ hours Wednesday as crews investigated a strange odor discovered in the rear of the store shortly before noon.

Yantic volunteer fire Chief Bernard Herz said the store was evacuated at 11:49 a.m. and was checked by fire and Norwich Public Utility crews, who determined it was not a natural gas leak. Herz said the problem was traced to a faulty rooftop heating, ventilation and air conditioning unit.

The store reopened shortly before 2:30 p.m.

Herz said the store would be ventilated with fans, and the remaining working HVAC rooftop units would recirculate the air in the building.