An elderly woman had her jewellery stolen when a burglar pretended to check the water.
A man visited the victim in her late 70s, telling her there was a problem with supplies in East Grinstead on Friday (November 9) morning.
She let him in to help her turn the water supply off, but then released her jewellery had been stolen.
Two gold rings, one which had a turquoise stone in the centre with diamond studded stars surrounding it and another with a blue sapphire and diamonds surrounding it, were amongst the jewellery which was taken.
Detective Sergeant Sian Harding of West Sussex CID said: "It is believed that while the man was in the kitchen with the victim another man entered the property through the front door which had been left ajar and stole jewellery.
"I would encourage anyone who receives a caller to check their identity. Don't be afraid to ask them to call back later or use the phone book to call the company and check if you have suspicions.
"We are appealing for anyone who saw two men acting suspiciously in the area on Friday morning, or anyone else who received a caller claiming to be from the water board to contact police."
The man is described as white, in his 50s, about 6ft, of heavy or stocky build, clean shaven, with short hair. He was wearing a light brown coat.
Anyone with information is asked to contact Sussex Police on 101 quoting serial 0617 of 9/11 or the independent charity Crimestoppers anonymously on 0800 555 111.