LONDON (AFP) - A sixth swan has tested positive for the H5N1 strain of bird flu at a nature reserve in south-west England, Britain's Department for Environment, Food and Rural Affairs (Defra) said Saturday.

The latest case comes after restrictions on the movement of poultry or other captive birds in a monitoring area around the Abbotsbury Swannery in the county of Dorset were lifted at 3:00 pm (1500 GMT) Friday.

Five other cases have been found in the same area since January 10.

"Defra has today (Saturday) confirmed that a sixth mute swan collected on 21 January as part of wild bird surveillance in the same area in Dorset has tested positive for highly pathogenic H5N1 avian influenza," a spokesman said.

The spokesman added that the development was "not unexpected" but there was no evidence to suggest the disease had spread to the wider wild bird population or domestic birds.

There were two outbreaks of H5N1 bird flu in Britain last year -- one at a turkey farm in eastern England in February and a separate one among birds in the same region in November.

Britain's first case of the virulent strain, which has killed more than 200 people worldwide since 2003, was in a dead swan found in a Scottish fishing village in 2006.

About 12 staff at the Abbotsbury Swannery are being monitored for signs of the disease and workers have been given a course of the anti-viral drug Tamiflu as a precaution. But the risk of infection is said to be low.