The Paparoa Howick Cemetery in Auckland is asking people who have a loved one at the cemetery to contact them - 20 bronze memorial plaques have been stolen, exposing the ashes.

Staff noticed the plaques missing yesterday from the columbarium wall and called police.

Auckland Council’s Manager Auckland Cemeteries Catherine Moore said the plaques appear to have been pried from the wall with a crowbar.

She said the ashes, which are inside plastic urns, have been re-labelled and stored elsewhere, but they need to get in contact with the families as some of the ashes have been there for years.

"We have managed to get hold of some families, but if there is anybody who hears this and they're concerned, then if they phone the number for the Southern Cemeteries team, they can speak to someone."

Ms Moore said it's a brazen act of vandalism that's very upsetting for families.

"Fortunately, it doesn't happen very often. These plaques have a very low scrap value, but they mean a lot to the families. They're an important part of that grief cycle."