More than 130 firefighters are working to contain a fierce fire that's broken out at a recycling centre in Melbourne's north.
The blaze is not yet under control at the Coolaroo facility on Maffra Street and a watch and act message has been issued for 18 suburbs in northern Melbourne.
It's understood weather conditions are not helping the fire crews after the wind picked up in the area, fanning the flames and blowing ash to areas in Flemington, the CBD and Docklands, which is 17 kilometres away.
Producer for radio station 3AW, Michael Hilder, said "it's literally raining ash" while he was in Collins Street.
Piles of plastic and paper have been burning for hours while the 80km/h winds are blowing the smoke south.
One woman told 3AW she had ash blown into her eye in Pascoe Vale, more than 10 kilometres away from the blaze.
Anyone located in the affected areas is advised to take shelter indoors immediately and to close all exterior doors, windows and vents and ensure that heating and cooling systems are turned off.
Factories near the Coolaroo blaze have been evacuated, while others have been locked down, with workers told to stay indoors and turn off the air conditioning.
At least 30 fire trucks are at the scene.
Crews were called to the Maffra Street factory at 8.44am, when it's believed the fire broke out in a pile of recycled materials outside the factory.
The Environment Protection authority is on the scene preparing to deploy air monitoring equipment
Fire crews faced a problem when the water pressure dropped as they plugged their hoses in this morning, but it was quickly fixed.
"We're working hard to protect [other businesses] and confine the fire to the plastic and paper recycling plant that we have here," Acting Deputy Chief Officer Ken Brown said.
Clarissa Garrow works directly across the road from the fire and she says the blaze is "insane".
"No one can get in and no one can get out," she told AAP.
"It's really bad.
"Ash and papers are flying everywhere."
Maffra Street is currently closed with emergency services warning locals to avoid the surrounding area.
This is the recycling centre's third major blaze in 2017, with another one in February needing 130 firefighters to bring it under control.
The alert covers Broadmeadows, Campbellfield, Coburg, Coburg North, Coolaroo, Dallas, Fawkner, Glenroy, Hadfield, Jacana, Meadow Heights, Oak Park, Pascoe Vale, Pascoe Vale South, Roxburgh Park, Somerton, Strathmore and Westmeadows.
Fire crews believe they’ll remain at the scene for most of the day due to the water only just reaching the flames.