Firefighters remain at the recycling plant in Smethwick, where crews have been controlling a blaze for more than 54 hours.
The fire, which destroyed 100,000 tonnes of plastic, was started when a drifting Chinese lantern landed in the yard.
Some MPs from the Midlands are calling on tougher regulations to limit damage caused by Chinese lantern.
Northamptonshire's Arson Task Force is warning local residents about floating lanterns following the fire at a Smethwick recycling plant.
Around 50,000 tonnes of plastic recycling material and a factory is on fire in Smethwick.