Along 1-40 west of Flagstaff, dozens of cars and trucks were involved in collisions or slid off the highway as snow began falling Tuesday afternoon. A stretch of the highway between Williams and Ash Fork was closed intermittently. Snowy and slippery conditions were also reported on I-17 north of Sedona.
The crashes near Casa Grande and a second set a dozen miles further south near Pichaco were triggered by dust kicked up from nearby farm fields. Dust and thick gray smoke from burning vehicles billowed across the flat sprawl of farms and desert.
In all, 22 vehicles were involved in the crashes, including nine commercial trucks. Authorities said six people were taken to Phoenix hospitals with undisclosed injuries, and one other person was treated and released.
Edgar Ivan Medina Vargas of Iowa City, Iowa, was among those killed. He slowed suddenly because of the dust storm, and his pickup truck was struck from behind by his father's large commercial truck, said Arizona Department of Public Safety spokesman Bart Graves.
Also killed were a brother and sister in a Jeep, Mark and Katie Eide of Casa Grande. He was 14 and she was 17, Graves said. Authorities say the siblings were headed to a restaurant at Picacho Peak.
The westbound lanes of I-10 were reopened by mid-afternoon, but state engineers will need to inspect the eastbound lanes before allowing traffic to resume, 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.