Residents of Melbourne's north are being warned of significant smoke as firefighters battle to contain a blaze which has ripped through a pasta factory in Somerton.

The first Metropolitan Fire Brigade trucks were on scene within minutes of being called to the fire on Fillo Drive at 12.30pm on Saturday, finding the 80 metre by 30 metre building already "well alight".

The MFB said in a statement that firefighters made sure the building was evacuated before beginning "an aggressive attack on the fire" while wearing breathing apparatus.

But after reports that some of the tilt-slab wall had collapsed, "all firefighting is external to
the premises," the statement read.

As of 2.25pm, 34 fire trucks were on scene and the fire was yet to be brought under control.

More to come.