A severed head has been found in a quarry in Cambridgeshire, police said.
A worker at the site in Mepal made the discovery on Monday afternoon and officers from the region's major crime unit have launched an investigation.
Police are trying to establish how long the remains had been there.
A spokeswoman for Cambridgeshire Police said: "We were called at about 3pm yesterday (May 16) afternoon with reports of the discovery of a human head at a quarry in Mepal.
"Officers from the Bedfordshire, Cambridgeshire and Hertfordshire major crime unit are conducting inquiries, both locally and across the county borders."
A spokesman for Mick George Ltd, the company that runs the quarry, said: "We are working closely with the police and providing them with all the information they need to undertake their investigations. At this point we cannot provide any further comments."
Detective Inspector Jerry Waite, from the Bedfordshire, Cambridgeshire and Hertfordshire major crime unit, said: "We are conducting inquiries both locally and across the county borders, and would urge anyone with information about the finding to contact us.
"At this stage we do not know if the head is male or female, however we have got officers carrying out searches at a site in Sharnbrook, Bedfordshire, as we believe this is where the remains may have come from."