(Waldport, OR) -- The investigation continues into what's causing balls of tar to wash up on Oregon and Washington beaches. The U.S. Coast Guard, Oregon Department of Environmental Quality and the Washington Department of Ecology are working under a Joint Operations Center. They know the tar balls are petroleum based, but they don't know the source. There have been no reports of spills from ships. Several birds are being treated for exposure to the oil. Three Common Murres were cleaned and released on the northern Washington Coast.