A major fire at a wood recycling plant in Tipton was started deliberately, West Midlands Fire Service says.
More than 30 firefighters tackled the blaze which broke out on Bloomfield Road on Sunday afternoon.
The force says it reviewed CCTV footage which shows the fire was an act of arson.
Two fire engines remain at the scene damping down and are expected to be there throughout the night.
Firefighters are still at the scene of a major fire at a recycling plant in Tipton.
One water jet is still in use this morning as crews tackle the blaze. Residents living in the area have been warned to keep their doors and windows closed due to the amount of smoke.
The #tiptonfire is still causing large amounts of smoke in the area, residents need to keep their doors and windows closed.
Station Commander at West Midlands Fire Service, Neil Griffiths, says there are 30 firefighters at the scene of a fire at a recycling plant in Tipton.
Crews working hard with difficult condition http://t.co/FV5AMURTH5
We are dealing with a significant fire at a recycling plant in Tipton with 6 appliances