Fire officials are working to determine the cause of a blaze that burned 30 to 40 vehicles in a Kent wrecking yard early Tuesday morning.

Firefighters responded to a metal recycling yard, located in the 26100 block of 78th Avenue South, around 4 a.m., said Puget Sound Regional Fire Authority Capt. Joe Root. Some of the vehicles had already been crushed or processed, he said.

No employees or firefighters were injured, and officials had the fire under control by about 5:50 a.m.

“The cars were still smoldering, and (firefighters) were working on hot spots that continued for several hours,” Root said.

Crews faced two challenges, he added — working around such a large stack of cars, and preventing hazardous material runoff from the vehicles, “especially with the large amount of water that flowed on-site,” Root said. Fortunately, he said, the facility had three retention ponds that firefighters used to collect runoff.

He didn’t have any more information about the cause of the fire.