A pair of beavers that were introduced to the Forest of Dean in Gloucestershire in a bid to tackle flooding have been replaced amid fears they could be infected.
There are fears the two beavers, which were introduced in July last year, may be carrying a deadly parasite called Echinococcus multilocularis.
It comes after a different group of beavers imported into the UK from the same area of Germany as the Forest of Dean mammals tested positive for the disease.
Left untreated, the parasite - which acts like a tumour - can spread to humans and other wildlife through the ingestion of infected eggs.
A spokesperson for the Department for Environment, Food and Rural Affairs (Defra) said the two beavers have been moved to a secure site for testing.
In the meantime, two other beavers - which have already been checked and cleared of the disease - have been introduced to the Forest of Dean, to continue with the project.
Beavers became extinct in the UK around 400 years ago, after being hunted for their fur and meat.
Conservationists reintroduced the two mammals last year in the hope they would provide a natural solution to the flooding problem in Lydbrook.
It was hoped they would build dams which would stop the storm water rushing down the steep-sided valley.