A woman who bought a box sight-unseen at an unclaimed property auction got a shock when she opened it and found a human skull, police said.

The woman turned the skull over to police, who said it was relatively clean and don't believe foul play was involved.

Phoenix police spokesman Sgt. Joel Tranter said officials were investigating where it came from.

"There's no indication the skull is connected to a crime," Tranter said. "It's possible it was part of a medical display."

The unidentified woman bought the item Tuesday during a closed-box auction at a self-storage facility. At such auctions, buyers don't know what's inside the boxes they're purchasing.