Firefighters were called out to tackle a large fire at an industrial estate in Peterlee.
Crews rushed to the blaze at the Peterlee West industrial estate after receiving reports at about 4.30am on Monday.
Eleven fire appliances attended the scene including the aerial ladder platform along with crews from Tyne and Wear Fire and Rescue Service and Cleveland Fire Brigade.
At its height, 50 firefighters were tackling the blaze in two adjoining units.
Nobody is believed to have been injured as a result of the blaze but people living in the area were urged to closed their windows.
Incident commander, County Durham and Darlington's group manager Rob Cherrie, said the fire is contained.
He said:"Three crews continue to fight the fire which is now contained and we have scaled back our resources at the scene.
"I would like to thank our crews and the firefighters from our neighbouring services for a swift and professional response in difficult circumstances."
Crews are expected to be at the scene throughout the day.
