Three dead white-clawed crayfish were reported in the River Thet
A warning has been issued to river users following a suspected outbreak of crayfish plague in Norfolk.
Three dead native white-clawed crayfish were reported in the River Thet at Thorpewood caravan site last week.
They are being analysed to see if they were infected with the highly virulent fungal disease crayfish plague, carried by the north American signal crayfish.
River users are urged to clean and dry their equipment, or disinfect it, before using in another river system.
Native crayfish were formerly widespread but the disease has already wiped out large populations in England and Wales.
The disease is spread by affected crayfish or, more commonly, equipment such as fishing nets, footwear, boats and farm machinery being transferred from infected waters.
Nina Fielding, from the Environment Agency, said: "This suspected outbreak is really worrying for the future of our native crayfish.
"There are only a small number of these endangered animals left in the Great Ouse catchment. If members of the public notice dead crayfish in any other rivers, please let the Environment Agency know as soon as possible."