The European Union's animal health laboratory in the United Kingdom has officially confirmed three dead swans found in Bulgaria were infected with the lethal H5N1 strain of bird flu, the country's agriculture and forestry ministry said on Monday.

Swans found at the Durankulak Lake in the Varna region and at a Burgas beach have tested positive for the deadly virus, the ministry said.

The veterinary authorities have already sealed off an area of 3 km to 10 km away from the sites where the dead fowl were discovered, said the ministry, adding that temporary disinfection points had been established.

Meanwhile, Health Minister Radoslav Gaidarski issued a statement claiming that as of Monday, there were no registered cases of human-infected avian flu.

The system created for monitoring bird flu in fowl and humans is effective and transparent, Gaidarski said, adding that it provided full and timely information on the country's situation surrounding the virus.

The minister also urged people not to trust any information that had not yet been confirmed by the government, while criticizing some local media for increasing tension with reports on cases undetermined.

According to reports from Sofia News Agency, four people have been tested for the deadly virus but all tests came out negative.

A young woman hospitalized last Friday in Bulgaria's second largest city of Plovdiv died on Monday morning after showing symptoms of bird flu.

Bulgaria's first bird flu case was reported in early February.

The H5N1 virus has killed tens of millions of birds since 2003, and there have been at least 165 confirmed cases of the strain spreading to humans, causing about 90 deaths, mostly in Asia.

Source: Xinhua