Bones believed to be human have been found at a remote location in the North York Moors National Park.
Police said the remains had been excavated near Chop Gate, south of Stokesley.
North Yorkshire Police said it was not yet clear if the bones belonged to more than one individual but they were not thought to be recent.
The force is working with a forensic archaeologist to try to establish their age.
A spokesperson said: "Although it is too early to say precisely how old these bones are, current forensic investigations suggest that they are not recent, and are likely to be several decades old.
"Specialists are being used to recover and examine them."
The force has asked people not to speculate online about the nature of the bones while work to recover and examine them continues.