More than 14 Fire Rescue Victoria crews and several CFA crews are battling a significant factory fire in Coolaroo.
The fire was reported at 6.51 am, with firefighters arriving at the Barry Road scene within six minutes.
Upon arrival, crews found the back of a 20-metre by 50-metre factory well alight.
Four people had evacuated the premises before crews arrived.
Firefighters immediately escalated the response, sending additional firefighters and appliances, and issued a community warning for smoke.
There is an Advice message issued for the suburbs of Campbellfield, Coolaroo, Dallas.
Smoke is visible in nearby communities, west of the Upfield Train Line rail crossing.
There is currently no threat to the community, but people should continue to stay informed and monitor conditions.
The fire is not yet under control.
