Scientists are trying to find out why millions of cockles are dying off the coast of west Wales.
They say there's no obvious reason why 6,000 tonnes of the shellfish off Gower have died.
Some people think it's because the water is polluted, but although scientists say it's possible, they think there could be other reasons.
They've ruled out a shortage of food, and are carrying out more tests today to find out what's going on.
In Britain, cockles are usually sold already cooked in jars, and are sometimes eaten with vinegar.
Cockles are a popular shellfish
One scientist, Matt Longshaw, said some infections had been found in the dead cockles, but none of them were harmful to humans.
Dr Ruth Callaway from Swansea University said it was possible the cockles were being affected by pollution.
But she added: "It's not a shortage of food and we've looked into the usual suspects, but there is no clear lead on what the reason could be."