The fire sent a plume of smoke up over southern Idaho.
Firefighters from multiple local areas are responding to a fire at B&T Auto Salvage on Old Highway 30 Monday afternoon.
Thick, black smoke could be seen from downtown Boise, and the first photos from the scene showed what appeared to be dozens of vehicles on fire.
There are no fire hydrants on scene, so several water trucks had to keep reloading and dumping into pools set up in the roadway.
At one point they had water issues, and the fire got away from crews and spread into a pile of tires.
Tire fires don't usually extinguish with just water, so crews have to use a special foam to help.
Fire officials on the scene estimate that about 100 vehicles burned. Investigators don't know how it started, but this isn't the first fire at this salvage yard.
Caldwell Fire said this has happened multiple times, and in some cases was caused by welding or cutting of car parts.
Crews still have to put the flames out before investigators can begin to look into the cause.
No injuries were reported, and no structures were threatened.