A industrial estate unit and lorry fire produced "a lot of smoke which can be seen for miles around".
Nine fire engines including two drafted in from Hertfordshire were fighting the blaze on the Globe Industrial Estate in Grays, Essex.
Essex Fire and Rescue Service said it had been called to the scene at about 14:30 GMT.
Firefighters were working to stop the fire spreading and neighbours were advised to close their windows.
Essex Fire Service said the fire was almost out at 17:00 GMT, but its officers would stay at the scene into the evening to extinguish hot spots.
Lots of scrap cars were involved in the fire and site staff had helped use diggers to move items so the fire crews could ensure they were completely out, the fire service said.