Vic metal yard fire still raging: MFB

Residents in a wide area across Melbourne's west are being warned to stay indoors and avoid contact with toxic smoke billowing from a major fire at a metal recycling yard.

Metropolitan Fire Brigade (MFB) crews were called to Sims Metal in Brooklyn about 4.40pm on Monday.

The fire remains out of control with around 90 firefighters still battling the blaze.

The MFB has issued a watch and act message for residents of Altona Gate, Braybrook, Sunshine, Sunshine West, Tottenham and West Footscray near the fire in McDonald Road.

"We're warning everyone in the suburbs up to 1km north of McDonald Road in Brooklyn to stay indoors, turn off their air-conditioners and close their windows," MFB spokesman Trevor Woodward told AAP.

Mr Woodward said the fire is in a large pile of metal that includes car bodies and discarded gas cylinders.

A crane and excavator are pulling apart the smouldering scrap pile to allow fire crews to get to the seat of the blaze.

The cause of the fire is not yet known.