A multi-car pileup in Utah left at least seven people dead over the weekend.

The multiple-vehicle collision, according to a Reuters report, happened on Sunday amid a dust storm that caused dramatic visibility issues in the area surrounding  Interstate 15 in Millard County.

In a statement most recently updated on Sunday evening, the Utah Department of Public Safety said the crash occurred around 4:30 p.m. near milepost 12. Per the department’s statement, at least 20 vehicles were involved in the incident, which resulted in multiple ground and air ambulances responding to the scene to help transport victims. As police have explained, no names of victims will be officially released until at least 24 hours after their families are notified.

A report from regional outlet KUTV, meanwhile, states that at least seven people were killed and 10 more were injured—some critically—during a pileup they report to have included 22 different vehicles. Children were also among those who were killed, per that report.

“We have vehicles all over,” Sgt. Cameron Rhodes of the Utah Highway Patrol said Sunday night, noting that he can’t recall in recent memory another example of a crash of this magnitude.

Image via Utah Highway Patrol

The latest updates include a determination from local authorities that five of the seven people who were killed were traveling together in one vehicle, while the two other deceased individuals were traveling in another vehicle.