PHOENIX - A sudden dust storm Tuesday spawned a series of collisions involving as many as 20 vehicles on Interstate 10 south of Phoenix, leaving at least four people dead.
Arizona Department of Public Safety officials said other casualties were airlifted to Phoenix hospitals with severe burns and other traumatic injuries.
A second series of accidents was reported farther south along the main route between Tucson and Phoenix. High winds and blowing dust were also reported west of Phoenix, and the highway patrol was urging drivers headed to Phoenix from California to drive with extreme caution.
The midday accidents led authorities to close I-10 between Phoenix and Tucson. It was expected to remain blocked for at least several hours.
Both directions of Interstate 40 in northern Arizona were also closed west of Flagstaff because of high winds and snow.
Traffic backed up for miles as I-10, a major east-west thoroughfare, was shut down in both directions at milepost 190 near Casa Grande. Dust and thick grey smoke from burning vehicles billowed across the flat sprawl of farms and desert.
The highway patrol said a commercial vehicle exploded, so a hazardous materials team was dispatched to the scene.
Video shot by a television helicopter showed the smoking hulks of several big-rig trucks, a passenger van and unrecognizable debris along about 300 yards of the eastbound lanes about 10 miles north of the junction with Interstate 8. In the westbound lanes, an injured person was loaded on a medical helicopter.
The highway was likely be closed in both directions for the better part of the day as state engineers look at the roadway, said Officer Robert Bailey, a Department of Public Safety spokesman.
"ADOT engineers have to get out there and examine the pavement and see if it's OK to be driven on after these fires," Bailey said.
The storm arrived fast and furious Tuesday morning, said David Bridger, a spokesman for the city of Casa Grande.
"This one came on so very, very quickly," Bridger said. "We knew it was something pretty serious coming. It is absolutely a major, major wind storm down here."