Dandenong fire: Massive blaze breaks out in Melbourne suburb

A massive blaze has engulfed a factory, blanketing Melbourne's skies in thick black smoke, sparking an urgent watch and act alert from authorities.

Dozens of firefighters are battling the out of control inferno at an industrial site in Dandenong South in the city's south-east.

A paint factory on Superior Drive burst into flames shortly before midday Friday. 

Multiple buildings are on fire with the sound of explosions also heard, according to witnesses.

The blaze is still burning out of control with strong winds blowing smoke to the south of the fire.

Authorities issued a watch and act message for residents in Bangholme, Dandenong South and Lyndhurst to stay indoors.

'Anyone located in the industrial estate in Dandenong South surrounding the Hammond Road area should take shelter indoors immediately,' the alert states.

Residents in surrounding suburbs should shut all doors and windows, turn off heating and cooling systems and keep pets indoors.

Police remain on scene. 

'At this stage the situation is ongoing. Surrounding streets have been closed and nearby businesses evacuated,' a spokeswoman said.

Motorists are urged to allow extra time and use Frankston-Dandenong Road or EastLink as an alternative routes .