Police are unable to determine whether a severed head found in a Cambridgeshire quarry belongs to a man or a woman.
The results of a post-mortem examination have come back inconclusive, although police believe the person died before 1 January, 2015.
Detectives from the Bedfordshire, Cambridgeshire and Hertfordshire Major Crime Unit are continuing to work with specialists to establish the gender and identity of the remains.
Police say no other body parts have been found, and investigators are not linking the discovery of the head with two women who have been reported missing in the region.
The head was found in the small village of Mepal, near Ely, by a staff member at the quarry on Monday afternoon.
A map showing the location of Mepal Quarry and Sharnbrook, from where the remains are thought to have come
The severed head was found on Monday at a quarry in Cambridgeshire
An unnamed quarry worker told the Bedfordshire On Sunday newspaper that his colleague found the remains when he took the cover off a skip he had just transported back to the site.
The worker said: "He took the cover off and spotted something straight away.
"His first thought was that it was a mannequin's head.
"But then he realised it had eyebrows and hair, and suddenly clicked that it was actually a woman's head.
"He said it had blood all over and was covered in dirt, but didn't look like it had disintegrated."
:: Anybody with information is asked to contact the Major Crime Unit on 101 or Crimestoppers on 0800 555 111.
