A 17-year-old boy was pronounced dead at University of Arizona Medical Center after he crashed into a wall on the Twin Peaks Road off-ramp west of Interstate 10.
He was not wearing his seatbelt, said Capt. Adam Goldberg, a Northwest fire spokesman.
Another 17-year-old passenger in the car, who was wearing his seatbelt, had serious injuries but was in stable condition, Goldberg said.
Police are investigating what caused the boy to lose control of the car and hit the wall head-on.
The Twin Peaks interchange is closed and traffic is backed up due to the crash.
Traffic in the area is being diverted onto the frontage road.
Drivers heading east toward I-10 from the Silverbell and Coachline roads area will be diverted south onto the frontage road from Cortaro Road, according to the Marana Police Department.