Firefighters are continuing to battle a fierce blaze at a Broadmeadows tyre recycling plant, which has sent a thick smoke plume across the city.

A pile of tyres at an industrial site on Maygar Bvd in Broadmeadows caught fire about 9am, producing a smoke column that can reportedly be seen as far as 75km away.

(9NEWS)

More than 50 firefighters aided by water-bombing helicopters are still battling to get the inferno under control.

The Metropolitan Fire Brigade issued the Watch and Act warning for people in Broadmeadows, Campbellfield, Coolaroo, Dallas, Fawkner, Gladstone Park, Glenroy, Gowanbrae, Hadfield, Jacana, Lalor, Meadow Heights, Reservoir, Thomastown and Westmeadows.

(9NEWS)

Firefighters are advising anyone within the affected areas to shelter indoors and to make sure all doors, windows and vents are shut and all heating and cooling systems turned off.

They have also advised people to avoid the area and Maygar Boulevard and Park Street, which are both partially closed.

(Alan Lang, Supplied, 9news.com.au)

The 3000m² blaze, which has already consumed more than 120,000 tyres, is producing toxic smoke, which is headed towards the Hume Highway, with northerly winds of up to 15km/hour expected throughout the afternoon.

MFB deputy chief officer David Youssef said despite the warnings, he did not believe it posed a danger to the community.

(9NEWS)

“We understand that people will be concerned about the smoke that they see ... we really just want people to stay indoors and close their windows,” he said.

“All smoke is toxic but at the moment, because of the wind conditions, fortunately it is not coming down to ground level so we don’t have any significant concerns for the community.

(Chris, supplied, 9news.com.au)

“We would ask people to continue to monitor the media and maintain a watch on what’s going on.”

Thick plumes of billowing black smoke from the blaze have been sighted across the city, with one photograph showing a Qantas jet dodging the airspace above the fire.

(Zane D'Silva, supplied, 9news.com.au)

The cause of the blaze at present remains unknown.

Up to 80 firefighters will continue to fight the blaze through the night, with stronger winds posing an extra challenge.

(Sonia Jajo, supplied, 9news.com.au)

Authorities say the fire could burn anywhere between 24 and 36 hours.