ABOUT 50 staff at Cobden's Fonterra factory were evacuated after a hazardous ammonia leak about 1.15pm on Tuesday.
Two CFA units attended from Cobden, while a hazardous materials unit from Warrnambool was requested but not required as staff contained the leak at 1.46pm.
A Fonterra spokeswoman said no injuries were sustained, however, Ambulance Victoria confirmed four patients had been assessed on site with mild headaches or dry throats.
"Earlier today, Fonterra Australia’s Cobden site in southwest Victoria experienced an ammonia leak due to a valve malfunction," the spokeswoman said.
"The site and all staff were immediately evacuated and relevant authorities called to the site.
"The problem was quickly isolated and has now been resolved with no injuries to personnel on site.”
By 1.54pm the air status was much clearer and at 2pm CFA were no longer required at the scene.
The Victorian WorkCover Authority was notified and is aware of the incident.
The CFA advised there was no threat to the community, but people should avoid the area.