A 4-year-old boy died and his 2-year-old brother was seriously injured in a three-car crash on eastbound Interstate 10 in west Phoenix late Tuesday morning.

The Arizona Department of Public Safety said a Dodge Challenger struck the rear of the Toyota Corolla carrying the boys near 43rd Avenue shortly after 11 a.m. The Toyota then hit a Chrysler Pacifica. The older boy died after being taken to a hospital; his brother was taken to another hospital with injuries that were not life-threatening.

Both boys were buckled in the back seat, the department said. The 4-year-old was in a booster seat, and the 2-year-old was in a car seat. Their mother, who was driving, was not hurt. The Challenger’s driver and a passenger in the Chrysler had minor injuries.

Troopers were interviewing the Challenger’s driver and investigating the cause of the crash, including whether alcohol or drugs played a role. Eastbound I-10 reopened shortly before 3 p.m.; westbound traffic was unaffected.