The Sweetwater County Sheriff's Office has warned of an ongoing "explosion threat" at the crash site, where a tractor carrying explosive transformers was reportedly involved in the pile-up

Wyoming Highway Patrol troopers said that the crash involved semi-trucks and passenger vehicles, and added that the strong heat was causing tires to explode

The crash occurred at 11:37 a.m. under a snow-dusted hill in Green River, Wyo., according to the State Transportation Department. By 5 p.m., the tunnel, which leads traffic west on Interstate 80, had been evacuated and the scene had “been contained,” the department said in a statement.