Arson suspected in Melbourne factory fire

A suspicious Melbourne factory fire involving fuel drums forced the evacuation of nearby businesses and shut down a train line.

The blaze in Broadmeadows sent toxic smoke blowing across Campbellfield on Monday night and led to the evacuation of surrounding businesses and suspension of train services.

Victoria Police say an arson chemist is expected to visit the factory on Tuesday.

A wall of the factory has collapsed and other walls are severely damaged, the MFB says.

The blaze, spotted about 8pm on Monday by a police helicopter on routine patrol, took 70 firefighters more than three hours to bring under control.

Surrounding businesses were evacuated as a precaution and a watch and act message was issued for nearby suburbs.

Trains on the Upfield line were suspended and the EPA Victoria was consulted due to wastewater from the fire entering a nearby creek.

No one was injured.