Around 50,000 tonnes of plastic recycling material and a factory is on fire in Smethwick.
West Midlands Fire Service says around 150 firefighters are at the scene on Dartmouth Road which it is calling a "major incident."
Smoke is rising 6,000ft into the air and can be seen across Sandwell and Birmingham.
Dartmouth Road, Halfords Lane and Brasshouse Lane have been closed and motorists are being urged to avoid Junction 1 of the M5 if possible.
The fire service says it has received more than 300 999 calls about the blaze and is warning to only call if there is an emergency.
It is asking residents near the fire to keep windows closed.
It is thought fire crews will be at the scene for days.