BRUSSELS/CONSTANTA (AP) - The European Union on Saturday confirmed that cases of bird flu found in wild swans in Bulgaria were caused by the highly pathogenic H5N1 virus.

“The disease was detected in wild swans in the Bulgarian wetland region of Vidin, close to the Romanian border, last week,” the European Commission said in a statement.

It said tests conducted by the EU Reference Laboratory for Avian Influenza in Weybridge, England, have confirmed the presence of the H5N1 virus. The presence of the virulent virus is causing concern it will mutate and cause disease among humans and a possible pandemic.

Meanwhile, two more cases of suspected bird flu have been found in swans near a lake in northeastern Bulgaria, close to the Black Sea.

The Bulgarian Health Ministry tried to calm fears by saying that so far no humans had caught the virus directly from wild birds.

“The incubation period for the disease has passed and there are no reports of people infected with the bird flu virus,” the Health Ministry said.

Police had already restricted the traffic around Shabla Lake at the end of January,after about 130 coots were found dead in the region. Those birds, however, were not infected with bird flu, according to tests.

Agriculture Minister Nihat Kabil explained that all regions where bird flu cases have been confirmed would be quarantined. He said that some 200 samples from domestic fowl in the area where the dead swans were found have all tested negative.

Yesterday Romanian authorities said they had detected an H5 subtype of the bird flu virus in domestic fowl in the country’s southeast. The virus was detected in preliminary tests on samples from a household farm in the village of Topraisar, near the Black Sea, said Grigore Mertoiu, who heads the local animal health agency.