An outbreak of bird flu has been confirmed at two turkey breeder farms in eastern England but the strain poses only a very low risk to human health, British turkey farmer Bernard Matthews said on Thursday. The company said Britain's agriculture ministry undertook tests after an unusual drop in egg production at two of its farms.

The farm ministry, in a separate statement, said laboratory results had confirmed the presence of bird flu but ruled out both the H5 and H7 strains.

"Further laboratory tests are in progress and results are not expected for some days yet," the ministry said.

A lethal H5N1 strain of bird flu has killed more than 250 people since 2003 and millions of birds have either died from it or been killed to prevent its spread.

Bernard Matthews was hit by an outbreak of the H5N1 strain at a farm in eastern England in early 2007.

There have also been several outbreaks of a virulent H7N7 strain in Europe during the last few years.