POLICE patrols have been stepped up at Calderdale burial grounds after a pig's head was left on a Muslim grave.
Several other graves were daubed with graffiti in the attack at Exley Cemetery, Exley Lane, Elland, on December 9.
The head, which was on a stick driven into the grave, was discovered by a funeral director the next day.
The attack has outraged the community, particularly because Islam forbids its followers from eating or touching pork products.
Chief Insp Bill Hall, of Calderdale Police, said the stick had been tested for DNA.
The area has been searched and house-to- house inquiries have been carried out to find out where the head came from.
"We are dismayed at the people who have carried out this vile attack and we are treating it very seriously," he said.
"We have put additional patrols at all places of burial across the whole of Calderdale.
"The motive for this attack is not clear and the graffiti has not led us to any particular group."
Anyone with information is asked to call the police on 01422 337059.