The skeletal remains of five homicide victims found recently on the Tohono O'odham Nation are male and at least three were shot, the county's chief medical examiner said.

The Pima County Office of the Medical Examiner is trying to determine the type of injuries sustained by the other two, but Dr. Gregory Hess said he suspects it will also be gunshot wounds.

Border Patrol agents discovered the remains in a rocky area near Sells on May 28. Some of the remains were wrapped in tarps and covered with rocks.

The tribe's Police Department is investigating the deaths, Police Chief Joseph Delgado told The Associated Press.

The bodies had been in the desert for between six and 12 months, Hess said.

No one has been identified, but due to clothing and personal effects, Hess said it's presumed they were foreigners.

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The next step is to try to identify the bodies, Hess said. "It's very difficult for law enforcement to do anything if you don't know who the decedents are."