Illegal treasure hunters, known as “night hawkers,” are damaging the area around Hadrian’s Wall, AFP reports.

The lawbreakers are using metal detectors and excavating the land surrounding the 1,900-year-old Roman wall, attempting to remove important ancient artifacts.

National Crime Advisor for English Heritage, Mark Harrison, said the work of the criminals is no different to stealing: “Just as it is against the law to break into someone’s house and steal their possessions, so it is illegal to damage land and steal valuable historical artefacts.” He added, “The objects they are stealing belong to the landowner, in this case the National Trust, and the history they are stealing belongs to all of us.”

Hadrian’s Wall was built in AD 122–130 by the Romans as a defensive fortification. Stretching across 73 miles of Northern English countryside, it is one of the UK’s most visited tourist attractions, bringing in thousands of visitors per year. In 1997, the ancient area was made a UNESCO World Heritage Site. It is now a crime to use a metal detector there without special permission.

The rise in “night hawking” is thought to be caused by recent publicity surrounding the unearthing of a number ancient treasure troves, such as the discovery of an Anglo-Saxon coin hoard in Buckinghamshire (see $2 Million Anglo-Saxon Coin Hoard Discovered in Lenborough, Buckinghamshire).

Northumbria police are still searching for the wrongdoers.