Steve Vincent, Area Commander of the West Midlands Fire and Service, has told ITV News Central that firefighters will remain at the scene of the fire in Smethwick for the next few days.
Two hundred firefighters tackled the blaze at the recycling plant yesterday, with around 50 still on site today.
Mr Vincent said: "This was one of the largest fires that the West Midlands Fire Service has ever had to tackle."
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.