14/07/2017 9:10 AM AEST | Updated 14/07/2017 11:54 AM AEST

Coolaroo Blaze Blankets Melbourne In 'Toxic' Smoke As Four Hospitalised, Homes Evacuated

Around 160 firefighters and emergency crews continue to battle the out-of-control fire.

Melbourne residents were evacuated overnight as scores of firefighters continued to battle a massive blaze at Coolaroo recycling plant which has blanketed the city in thick, acrid smoke.

At least four people have been taken to hospital with respiratory problems from the fumes, as firefighters warn the out-of-control fire was likely to burn through the weekend.

The Metropolitan Fire Brigade (MFS) issued an evacuation order for 115 homes in the neighbouring suburb of Dallas at 8:11pm on Thursday night.

Masked police and SES crews door-knocked houses and evacuated residents, who were told to bring their pets, medications and mobile phones and securely lock their houses.

Forty-one people attended a relief centre, which was opened at the Aquatic Leisure Centre in Broadmeadows. SES crews and aquatic centre staff arranged the accommodation of evacuated residents with Hume Council footing the bill.

While there, eight residents were treated for smoke inhalation by paramedics, one of whom was taken by ambulance to Northern Hospital in a stable condition.

Residents in the surrounding suburbs of Broadmeadows, Campbellfield, the rest of Dallas, Fawkney, Glenroy, Jacana and Westmeadows were issued with a "watch and act" warning. They were told to stay indoors, close all exterior doors, windows and vents and turn off all heating and cooling systems.

The fire broke out at the recycling facility before 9am on Thursday. It is the third time this year that a major fire has broken out at the recycling facility, The Age reports.

Several nearby businesses were closed on Thursday, with workers sent home to avoid the toxic smoke.

Incident controller Mark Swiney told The Age that continued exposure to the smoke could affect people's health.

"We did atmospheric monitoring and in the area to the south of the fire we found that there were particulates in the air which are detrimental to people's long-term health," he said.

A spokesperson for Ambulance Victoria told HuffPost Australia that it has transported four people to hospital to be treated for respiratory problems associated with the fumes, after five '000' calls overnight and on Friday morning.

The Herald Sun reports that a four-year-old girl has also been taken to hospital for treatment.

Assistant Chief Fire Officer Ken Brown said that the Metropolitan Fire Service was working with the EPA and the local council to get the toxic fumes down to an acceptable level.

But firefighters have so far been unable to get the blaze under control, admitting it could take as long as three days to extinguish.

"It's a very deep-seated fire. That brings about a complexity within itself," MFB Commander Ken Brown told a community meeting at Broadmeadows on Thursday.

"The only way you're going to put that out, once you control the smoke, is to pull the piles apart. It's a limited space area so that makes it difficult to manoeuvre stuff around."

The plumes are blowing south towards Melbourne's CBD, but the Environment Protection Authority reported that air quality remained "very good" over Melbourne's CBD on Friday morning, according to Victoria's Environment Protection Authority.