Two horses were struck and killed by a pickup near Elephant Head and South Canoa roads early Sunday.
Pima County Sheriff's Deputy James Allerton said the horses had escaped from a nearby field and were struck around 4:30 a.m. The driver of the pickup was uninjured.
No citations were issued because "the responding deputy had no reason to believe that the driver had violated any traffic laws," Allerton said.
Karen Pomroy, president and founder of Equine Voices Rescue and Sanctuary, said speeding is a "major problem" in the area, which is open range.
"The next thing that's going to happen is a person is going to get hit and killed," she said.