Around 35 fire fighters are at the scene of a large fire at a scrap yard in Hitchin.
The fire broke out at Metal & Waste Recycling on Thursday morning on the Walsworth Industrial Estate.
Hertfordshire Fire Control service has advised people living nearby to keep their doors and windows closed.
According to the fire service, a large amount of metal recycling is on fire.
The police are urging people to avoid the area around Wallace Way and road closures are being put in place.