Investigations have begun in Cardiff with the death of 30 swans over a three week period
The Animal Health and Veterinary Laboratories Agency is investigating the birds' death and advises not to touch a dead bird with bare hands.
According to BBC, bird flu has not been diagnosed as cause of death.
The Animal Health and Veterinary Laboratories Agency (AHVLA) said: "Reports of increased levels of mortality amongst wild swans in the Cardiff area are being investigated as part of the Animal Health and Veterinary Laboratories Agency's Diseases of Wildlife Scheme.”
"Notifiable disease, including avian influenza, has not been diagnosed, but the underlying cause of these deaths is unknown at present. Investigative work is continuing."
Source: BBC News