The crash involved a recreational vehicle, three tractor-trailer trucks and three other vehicles. All of the vehicles except the RV were gutted by fires that broke out after the collision.
Police said that one driver, unable to see because of the dust, came to a stop and was struck in the rear on I-10 in Hidalgo County, six miles from the Arizona border.
The collision was the second this week involving multiple fatalities on I-10 in the southwest. On Wednesday, four passengers were killed when a bus traveling from El Paso to Los Angeles by way of Phoenix overturned in Blythe, Calif., near the Arizona line, after hitting a load of pipes spilled from a truck.
The highway begins on the Pacific coast in Santa Monica, Calif., and connects with I-95 in Jacksonville, Fla.
State police said the speed limit in the area of Thursday's crash was reduced because of damage to the pavement from the fires.