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.

Wyoming authorities are investigating a multi-vehicle crash on Interstate 80 near the Green River Tunnel that killed at least two people, sparked an active fire, caused major damage to the roadway and prompted a large-scale response from state, local and federal agencies.

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.