Huge plumes of smoke billowed from the site at Belraugh Road, Garvagh, on Tuesday afternoon.
The blaze was reported to the Northern Ireland Fire and Rescue Service (NIFRS) shortly after 14:00 BST.
Six fire engines from Coleraine, Dungiven, Maghera, Ballymoney and Limavady attended the scene.
The NIFRS said its fire emergency support service vehicle was also deployed, along with a command support unit from Kilrea and water tanker from Pomeroy.
Earlier on Tuesday evening, Alan O'Neill from the NIFRS said the fire had been brought under control.
"When we arrived there was quite a significant amount of vehicles involved and we increased our fire appliances to six at the scene.
"We have been there from shortly after twenty past two and we expect to be there for the next couple of hours."
Up to 600 vehicles have been damaged during a large fire at a car  dismantlers' yard in County Londonderry, firefighters have said.