Toxic smoke is blowing across Melbourne’s west and some residents have been told not to return home after a chemical explosion sparked a massive factory fire on Wednesday.

Firefighters are battling the blaze in Swann Drive, Derrimut, after the fire broke out shortly before 11.20am.

“The fire has involved a large chemical explosion, resulting in a large fire,” Fire Rescue Victoria said in a statement. “Specialist appliances are on scene, including aerial appliances.”

A watch-and-act warning was issued shortly after 1pm in Derrimut and the neighbouring suburbs of Albion, Braybrook, Brooklyn, Laverton North, Sunshine, Sunshine West, Tottenham and Truganina.

Residents in those suburbs have been told to close all exterior doors and windows. They were also urged to close vents in their homes and ensure heating and cooling systems are turned off. Residents not currently at home have been told not to return.

The toxic smoke is also being blown across to Melbourne’s eastern suburbs. Anyone affected is urged to take shelter indoors immediately.

Ambulance Victoria said paramedics arrived about 11.15am. No patients have been treated so far.

The surrounding industrial estate is also being evacuated by police along Swann Drive to Bliss Court. The Environment Protection Authority Victoria will also attend the scene.