People living in an apartment building in southwest Calgary are now back home after a carbon monoxide leak forced them out for a few hours.

Fire crews responded to a call in the 500 block of 22 Avenue S.W. around 10 p.m. MT Saturday. Carbon monoxide detectors immediately went off when crews entered the building, but responders believe they found the source of the problem.

"We fired the boiler up, with nobody in there of course, and then monitored carbon monoxide levels and they did come up again," said battalion Chief Alan Ball. 

Ball says the boiler will remain off until it can be fixed.

Crews are expected to work on that Sunday.