CFA was called to the incident at PFD Food Services in Rushdale Street about 6.45am today.
After a number of workers were evacuated from the factory, it was discovered ammonia was leaking from a refrigerated unit.
With the assistance of fridge mechanics, the leak was isolated and the incident was called under control just after 8.00am.
Five appliances and a number of support vehicles were on scene throughout the job. This included specialist hazmat detection units from Hallam and Dandenong.
It is believed the cause of the leak was a faulty valve within the unit.
Some workers, with complaints of breathing difficulties, were treated on scene by ambulance.
During the incident, CFA issued an Advice message for businesses and residents in the area to stay indoors. They have now been given the all clear to resume normal activities.