Tomb raiders who targeted a Denbighshire churchyard are suspected of looking for lead.
They are being hunted by North Wales Police after the tops were lifted off six 17th and 18th Century tombs at St Garmon's church in Llanarmon yn Ial.
But they left empty-handed when they discovered the tombs were empty as the coffins are buried underground, said county councillor Christine Evans.
Police called the raids a "mindless act of vandalism".
The break-in took place on Tuesday, and the alarm was raised the following morning by men carrying out work on a nearby house.
About £800 of oil from a tank at the church was also stolen and police are investigating whether this was carried out by the same people.
Mrs Evans said: "The stones were lifted off and the people who did this had clearly used lifting equipment.
"They obviously didn't realise that the tombs were empty with the coffins buried underground. We think they must have been looking for lead.
"It's absolutely appalling that someone should want to rob a grave, completely mindless and unnecessary."
Church warden George Flanagan said: "It's sheer desecration. To go to a churchyard and do this just beggars belief. It was obviously a planned robbery .
"They haven't damaged the stones, but when they lifted the tops off, the sides have fallen down.
"They must have been looking for lead coffins or artefacts.
"But to do this in the way they have suggests that they may have some success elsewhere."
Police have appealed for information and community support officer Ben Madeley said they were anxious to speak to anyone who was in the area at the time and noticed anything suspicious.
He said the offenders entered a property being built next door to the church but nothing was taken.
He said: "They then went into the churchyard and pushed over six raised gravestones.
"There has also been a quantity of heating oil taken from a tank at the back of the church although we do not know whether this occurred at the same time.
"We are taking this mindless act of vandalism seriously and can reassure the local public that a full investigation will take place and we will pursue all lines of inquiry to try and discover who is responsible."
Anyone with information is asked to contact North Wales Police on 101, 0845 6071002, or call Crimestoppers anonymously on 0800 555 111.