Contractors have unearthed a human thigh bone while laying a gas pipeline in Carmarthenshire.
Police put up a tent at the scene of the discovery at Lower St Clears
Police have cordoned off the scene at Carmarthen boat club, St Clears, erected a tent, and asked a Home Office pathologist to examine the bone.
Other bone fragments were found by contractors working on connecting liquefied natural gas (LNG) plants at Milford Haven to the UK gas supply.
Forensic archaeologists are trying to establish if there are more remains.
Det Chief Insp Martin Davies said the bone had been examined by a forensic pathologist, who confirmed it was human.
He said they had also found other bone fragments at the scene, as well as a number of artefacts such as bottles dating back to the 1950s.
"We've got no evidence of any burial site being at this location so there should not really be a body here," he said.
"it could be a missing person, we are going through all our records.
"We are also looking through previous murders to establish whether or not the bodies were recovered at the time."
An incident room has been set up at Carmarthen police station and the coroner has been informed.
"We would appeal to members of the public who may be aware of a person who has gone missing during this period (the 1950s) to come forward," said DCI Davies.
"We would also be interested in any local knowledge of the use of the site at this time."
Anyone with information can contact the incident room on 0845 3302000.