Between 200 and 300 people were told to leave a La Prairie sports arena Sunday evening after an ammonia leak was discovered.
Seven people, including two workers, were taken to hospital with minor injuries.
The arena and some nearby homes in the South Shore community were evacuated for the better part of the evening.
The people were taken to a community centre, and were able to return home around 11 p.m.
The CSST, Quebec's workplace health and safety board, is investigating the cause of the leak.