Sixty people evacuated a Derrimut pork processing plant due to a carbon monoxide leak on Monday 1 December.
Fire Rescue Victoria (FRV) said there were multiple casualties suffering the effects of carbon monoxide exposure.
Crews assisted by applying oxygen therapy to the patients until paramedics arrived on scene.
Firefighters entered the factory with gas detectors to take readings and assess the situation.
It was found the carbon monoxide readings inside the building were still dangerously high.
Crews ventilated the building until the carbon dioxide in the atmosphere dropped to safe levels.
The leak was found to have come from some meat preservation machinery.
The incident was declared under control at 1:41pm.
WorkSafe has been notified of the incident.
