SKM Recycling's facility in Coolaroo, 19km north of Melbourne, is up in flames for the third time this year. Authorities say it could take up to three days to fully extinguish the fire and the MFB plans to deploy a drone to determine what exactly is on fire.

Firefighters battling the blaze at the SKM facility in Coolaroo. (Photo: Twitter/@MFB_News)

Some 130 firefighters in about 50 trucks are reportedly at the scene fighting the blaze in windy conditions. And the wind has been a further bane, carrying ash and smoke to the CBD. According to The Age, callers to 3AW radio reported ash falling in Pascoe Vale, Flemington, Docklands and the CBD.

The fire broke out at 9am this morning and businesses south of the blaze were evacuated. A large smoke warning has also been issued for surrounding areas.

This is SKM's third fire at the site, after an incident in February and another last month.

The extent of the blaze can be seen in this ABC News video.