Illegal 'nighthawks' target historic Corbridge site
So-called metal detector "nighthawks" have damaged a Roman site in Northumberland.
The illegal treasure hunters have been targeting remains close to Corbridge.
Holes have been dug in the ground and it is believed artefacts may have been taken.
The site is a protected Scheduled Monument and only detectorists with written consent from Historic England are allowed to scan the area.
The group that looks after the remains has asked the public to keep an eye out for suspicious activity and to call the police.
'Cover of darkness'
Mike Collins, inspector of ancient monuments for Hadrian's Wall at Historic England in the North East, said a number of holes have been dug in the field near the remains.
He said: "We're assuming they've retrieved considerable amounts of Roman artefacts, such as coins or any metallic domestic items, but because they're acting under the cover of darkness it's difficult to quantify.
"It's very clear the activity is happening overnight when the detectorists can't be seen from the surrounding countryside.
"It's been an issue for decades, but we've had several instances in the last few weeks."
Patrols are carried out by an English Heritage security guard as well as local police officers, Mr Collins added.
A find known as the Corbridge Hoard was unearthed at the site in 1964 and shaped the understanding of how Roman armour was made.