Authorities said skeletal remains were found in the Arizona desert in a section where smugglers from Mexico bring in humans and drugs, according to Reuters. The investigators said foul play is still a possibility.

United States Border Patrol Agents found the five remains Tuesday, slightly hidden under rocks, explained the medical examiner for Pima County. They were found close to the Tohono O’Odham Reservation in the town of Sells. Sells is approximately 130 miles outside of Phoenix.

According to Chief Medical Examiner Gregory Hess, "It's not a typical migrant death site. Usually that's people laying under a tree because it got too hot, and they're on the surface of the ground and nobody tried to bury them."

"The remains were partially covered with rocks and we're not sure if that's an attempt to hide (them) or if somebody just buried them there for some other reason ... or whether or not that indicates foul play or what's going on," he added.

The investigation is being headed up by the Tohono O’Odham Police Department. They declined to offer comment on the situation. The Border Patrol unit located in Tuscon acknowledged the remains had been found but did not go into additional detail.

Hess explained that normal border-crossing deaths usually occur because of extreme heat or other factors. Arizona sits right on an area used by smugglers of both drugs and humans traveling from Mexico.

These remains do not indicate normal circumstances, Hess added.

Hess also said he had not figured out the gender, age or cause of death. He plans to perform the autopsies within the next week.