The National Park Service says it removed 24 dead ducks from the Capitol Reflecting Pool on Saturday.

Park Service spokesman Bill Line says officials believe the birds died from avian botulism. Line says the disease is not unusual among ducks, and tends to occur in the summer because it thrives in warmer water.

Officials have sent the ducks to a lab for testing. Preliminary test results from a group of dead ducks found two weeks ago in the Capitol pool show they likely died of avian botulism.

Line says ducks dying from avian botulism are being found in several other parts of country. He says there is no risk of the disease being passed to humans.