Forty dead swans, two black-headed gulls and one heron have been found dead on the River Stour in the last 10 days.

The number has jumped significantly from last Wednesday, when 15 swans were discovered in the waterway close to Sudbury.

The Sudbury Common Lands Charity said it suspects bird flu is behind the deaths.

The Department for Environment, Food and Rural Affairs (Defra) is carrying out testing on the animals to determine the cause.

"We're deeply concerned," said Ross Bentley, a trustee at the Sudbury Common Lands Charity.

"In the summer, we normally have around 60 swans in this area and, as the winter months approach, 100.

"So this is affecting large a portion of the population.

"With the rate at which they are dying and the symptoms they are displaying, we believe it is bird flu.

"We have informed Defra, but they are yet to respond. So we can't confirm that at this time."

Of the 40 swans, 37 have been recovered so far.

Many of the animals have been found at Brundon Lane mill pond - a hot-spot for dog-walkers.

Defra has issued the following advice to residents:

  • Stick to footpaths;
  • Keep dogs on leads;
  • Do not touch dead or sick birds;
  • Do not touch surfaces contaminated by droppings;
  • If you keep poultry, wash your hands and disinfect your footwear before tending to your birds;
  • Please report dead birds to Defra.

"Swans are very much a part of our local landscape and they're a well-known attraction for the area," said Mr Bentley.

"So this is a very challenging time for us all - particularly our rangers."

The news follows a series of bird flu outbreaks across Suffolk and wider East Anglia.

Defra has said wild birds are susceptible to a range of diseases and injuries and that not all of those found dead will have been infected with bird flu.

However, members of the public should call the Defra helpline (03459 33 55 77) if they find one or more dead bird of prey or owl, three or more dead gulls or wild waterfowl (swans, geese and ducks) or five or more dead birds of any species.

Although bird flu is potentially devastating to commercial poultry and wild bird flocks, Public Health England (PHE) advises that the risk to public health from the virus is very low and the Food Standards Agency advises that avian influenzas pose a very low food safety risk for UK consumers.