Human remains have been found in Llanymynech cave. John Haynes/Creative Commons

A police investigation has been launched in Powys, Wales, after human bones were discovered inside a Roman copper mine dating back 4,000 years.

Dyfed Powys Police said officers were called to the scene in the ancient Llanymynech caves after two men with metal detectors came across the remains.

Forensic experts are working to determine if the bones are old or more recent.

Sian George from Dyfed Powys Police told WalesOnline: "Police are investigating the discovery of what appear to be human skeletal remains in an area known as Llanymynech caves.

"This was unearthed as a result of metal detection activity being carried out on the site which was a Roman copper mine.

"The remains are being examined by forensic experts who will help us determine the significance of this find, and whether they could be archaeological."

The caves in Llanymynech were first mined during the Bronze Age. Slaves would work the mines with iron picks and shovels, being kept prisoner deep underground.

After the Romans left, the mine fell into disuse but it was revived in the 12<sup>th century.

A number of Roman artefacts have been found in the mine, including burials and a hoard of silver coins.