Wyoming environmental regulators say carbon dioxide bubbling up from the ground may have killed six ducks and polluted a stream.
The leak happened in an area where CO2 is injected underground to help revive an old oil field and boost oil production.
The Wyoming Department of Environmental Quality has ordered Anadarko Petroleum to identify and control the carbon dioxide leak into Castle Creek in central Wyoming. DEQ also is telling Anadarko to monitor the stream's acidity until three consecutive tests show normal pH.
Anadarko spokesman Dennis Ellis says Anadarko hasn't yet verified where the gas originated.