An inferno that is raging out-of-control in Campbellfield will last for days.
More than 80 firefighters are battling the blaze.
MFB chief officer Dan Stephens said the incident will be similar to a factory blaze in West Footscray last year.
“It took us the best part of a day to get that fire under control,” Mr Stephens said.
At this time, he said, the Campbellfield fire is surrounded but not yet under control.
Huge clouds of toxic smoke are spreading across Melbourne with warnings now in place within Campbellfield, Coolaroo, Somerton, Broadmeadows, Pascoe Vale and Coburg to stay indoors.