UPDATE: A large fire at a car wrecking yard at Campbellfield has been brought under control.
It's believed two workers have suffered burns in the blaze in Bolinda Road and paramedics attended the scene.
The MFB warns the fire has sent a large plume of black smoke over the Glenroy, Coburg and Fawkner areas.
Residents are urged to stay indoors and keep their windows and doors shut until the smoke clears.
EARLIER: Fire fighters are battling a factory fire in Campbellfield.
The blaze broke out in Belinda Road a short time ago.
Witnesses have reported hearing explosions.
Ambulance crews have been called to the scene and it's understood 2 people have suffered burns.