Blaze destroys Melbourne nut factory

A blaze has destroyed a nut factory in Melbourne's north with firefighters taking several hours to contain the fire.

Up to 80 firefighters were needed to contain the fire at the Campbellfield factory, which started before 2pm on Tuesday.

"Firefighters believe the building may be at risk of structural collapse and are employing a defensive firefighting strategy to bring the fire under control," a Metropolitan Fire Brigade statement said.

"The factory is mainly full of supermarket products and oils so there's not the industrial chemicals," an MFB spokeswoman said.

Residents are being asked to stay indoors, shut windows and doors and switch off heating and cooling systems.