Interstate 80 was closed in Green River after the crash and will likely remain so until at least Wednesday, officials said. The roadway runs from San Francisco nearly to New York City.

Investigators in Wyoming began sifting through the wreckage inside a highway tunnel Saturday after smoke, hazardous chemicals and structural concerns prevented them from determining how many people may have died in the fiery pileup.

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.