FLORENCE, Ariz. - Eight people were killed in a head-on collision south of Florence Wednesday night, according to the Arizona Department of Public Safety.

According to DPS, the crash involved a Chevy Suburban and a Buick. The crash happened on SR-79 at milepost 122.3.

PHOTOS: DPS released crash photos from the scene of accident that killed 8 people.

The Suburban had nine people on board when it was struck head-on by a Buick passenger vehicle, DPS said.

DPS said it's not known at this time why the Buick went "left of center" and collided with the Suburban.

According to DPS, the driver, front-seat passenger and five additional passengers of the Suburban were killed. Both the driver and front-seat passenger of the Buick were killed.

DPS previously said nine had died in the crash, but tweeted an update later in the day saying three people involved in the crash were in the hospital, one being in extremely critical condition.

DPS said passengers in the Suburban besides the driver and front-seat passenger were undocumented immigrants. Troopers are working with the Department of Homeland Security to attempt to identify and make next-of-kin notifications, which DPS says will take time to complete.

Both directions of SR-79 were closed, but reopened just after 4 a.m. Thursday.