A third wild swan had tested positive for the H5N1 strain of bird flu, a Polish laboratory said on Tuesday.

The swan was found dead Saturday in Torun, about 200 kms northwest of Warsaw.

Tadeusz Wijaszka, head of the Polish laboratory said tests showed "We have a third case of H5N1."

"H5N1 was detected in a third swan," Wijaszka said.

The H5N1 strain of bird flu was also detected in two dead swans in Torun on Monday.

Poland has sent samples to a European Union laboratory for further tests.