CINCINNATI: Crews are preparing to move into the next stage of cleanup of thousands of gallons of pipeline oil that leaked into a nature preserve.

Officials said Friday that crews were winding up the initial emergency response that focused on removing the heaviest concentrations of oil in the Oak Glen Nature Preserve west of Cincinnati. Officials hope to begin focusing on removing residual oil from individual sections of the preserve next week.

Federal officials estimate more than 20,000 gallons — about 500 barrels — spilled into an intermittent stream and an acre-sized marshy area that forms a pond in wet weather.

No problems have been detected with air quality or local water wells, but at least 20 small creatures —including crayfish, frogs and salamanders — contaminated with oil had died.