MUNDS PARK, Ariz. - The Arizona Department of Public Safety said a crash on Interstate 17 that killed four people Friday was caused by a wrong-way driver.

According to DPS, around 4 a.m. Friday morning, a Jeep was traveling southbound in the northbound lanes on the I-17 near Munds Park when it collided with a Nissan carrying a driver and three passengers.

The Jeep hit the Nissan head-on, killing all four of its occupants, DPS said.

The driver of the Jeep was injured and taken to the Flagstaff Medical Center. DPS identified him as 19-year-old Carlos Quinonez from Casa Grande.

The driver of the Nissan was identified as Christen Ebert, 26. The passengers included Richard Chum, 30, Gary Sindhu, 29, and Kouang Saefong, 30, according to DPS. All of them were from California.

The crash caused miles of slow traffic Friday morning.

DPS said the investigation is ongoing.

Wrong-way drivers have been a major safety issue in Arizona lately. In June, Governor Doug Ducey called on the state to "more seriously" address wrong-way driving and ordered thermal camera detection technology.

Installation of the wrong-way detection system started this weekend along the I-17 in Phoenix.

READ: New wrong-way detection system is now being installed in Phoenix