A human skull found in a Goodwill donation box in Arizona is believed to be "historic," and not related to a crime, police say.

The skull was placed in the donation box at a Goodwill in Goodyear, Arizona, a southwestern suburb of Phoenix, by an unknown donor.

It was discovered by Goodwill staff on Tuesday, who reported it to the police, per company protocol, and continue to cooperate with the police investigation, according to a spokesperson for Goodwill of Central and Northern Arizona.

Police responded to reports of the skull discovery and took possession of what was believed to be "an actual human skull" at the Goodyear Goodwill.

A photo provided by police shows the skull was covered with dark black spots, with the upper front teeth still attached and a false eye set on the left eye socket.

Is the Goodwill human skull part of a crime?

Goodyear Police Department said a human skull found in a Goodwill donation box was not believed to be related to a crime.

The skull was transported to Maricopa County Office of the Medical Examiner where it was found to be of "historic" origin.

The skull has no "forensic significance, meaning there appears to be no associated crime," said Lisa Berry, a spokesperson for Goodyear police.

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Will the human skull be available at Goodwill?

It was unclear if the skull would be returned to the Goodwill store in Goodyear or what it would be priced at.

A spokesperson for Goodwill Industries International could not be reached for comment and a manager with the store declined to speak with The Arizona Republic, part of the USA TODAY Network.

The investigation was ongoing.