A man visited Riplingham Road cemetery, where his parents are buried, at the beginning of April 2013 and found that the area was overgrown.
The man and his wife, who live in West Yorkshire, went back to the cemetery on 23 May to cut back the overgrown ivy, when they noticed that the white marble surround and white chippings on the top of the grave had been removed.
Humberside Police would like to speak to anyone who may have any information about this incident. Please call 101 quoting reference 1979022/13 or call Crimestoppers anonymously on 0800 555 111.