HONG KONG — Two dead birds were discovered at an Olympic equestrian venue in Hong Kong, and authorities were testing whether they were infected with the bird flu virus.

The birds were found last week, equestrian competition official Mark Pinkstone said Monday.

The H5N1 bird flu doesn't pose a threat to horses, but can be lethal to humans. Hong Kong has struggled with the bird flu for years and six people died during the biggest outbreak in 1997.

The Olympic equestrian events, to be held between Aug. 9 and 21, were moved from Beijing to the former British colony because of a rash of equine diseases and substandard quarantine procedures on the mainland.