"Unified Command has reinstated the shelter-in-place order for a one-mile perimeter around the incident. While crews were attempting to remove the load from the commercial vehicle, gassing occurred. Interstate 10 remains closed in both directions between Kolb & Rita roads in Tucson," the AZ Department of Public Safety wrote in a Wednesday update.

Residents were warned to avoid the area and seek alternate routs of travel, while anyone within a one-mile perimeter of the incident has been instructed to turn off air conditioning and heaters in order to avoid bringing in outside air.