Plans to tackle heritage crime have been extended to protect historic sites across Wales.
Archaeologists, national park officials and Dyfed-Powys Police officers were due to hold a meeting at the weekend to discuss concerns about vandalism.
The conference was cancelled because of coronavirus fears but was due to identify areas at risk of damage and offer training to protect remote sites.
Police, Cadw wardens and park rangers will regularly patrol sites.
There are thousands of heritage sites around Wales, ranging from stone age monuments to World War Two buildings.
Incidents include the daubing of a Neolithic burial chamber with animal blood and bluestone fragments from rocks linking Pembrokeshire with Stonehenge being sold online.
A heritage watch scheme was launched by Pembrokeshire Coast National Park two years ago.
Dyfed Archaeological Trust and Dyfed-Powys Police have also joined the scheme, establishing a team of 10 officers trained in dealing with reports of crimes at monuments.
'These monuments cannot be replaced'
Tomos Jones, archaeologist for the Pembrokeshire Coast National park says the types of crimes which threaten the sites were extremely varied.
"At Pentre Ifan we found daubing using animal blood - possibly the result of some ritual," he said.
"There are regular problems with fires on what are remote sites in the Preseli Hills, where we now know stones for Stonehenge were cut.
"There have been cases of people chipping away the remaining bluestones and damaging cairns.
"Some of the bluestone fragments have appeared on eBay."
Insp Reuben Palin, Dyfed-Powys Police lead for heritage crime, said: "We are fortunate to have a number of ancient monuments and archaeological sites in our force area that are of immense national and international significance, and attract visitors from across the world.
"These monuments cannot be replaced, and it is part of our duty to ensure they are protected."