A plastic bag containing what appears to be a human skull was found at a police parking lot in Nara Prefecture on Thursday morning.
Local police plan to analyze the skull at the Nara Medical University on Friday, officials said.
According to the Kashihara Station of the Nara Prefectural Police, a 56-year-old lieutenant stationed at a police box in the village of Asuka picked up the plastic bag placed at the parking lot around 8:30 a.m.
In the bag was what appeared to be a human skull lacking a jaw and teeth, the officials said.
No skin or hair was attached to the skull, and there were no bloodstains.
There were no signs of scars or any indications that the skull had been severed, they said.
The plastic bag is believed to be one of those distributed to customers at a car parts dealer that has outlets in the cities of Kashihara and Yamato-Koriyama in the prefecture.
The lieutenant said he had noticed the bag at the parking lot when he passed the site around 1 p.m. Wednesday. He did not touch it because he thought it was a garbage bag waiting for collection, police said.