DENVER (AP) — A worker at a federal laboratory in Colorado intentionally manipulated test results for years, possibly tainting research that includes toxic metals in the Everglades, uranium near the Grand Canyon and coal in Afghanistan, investigators say. The falsified data from a U.S. Geological Survey lab may have affected 24 coal, water and environmental research projects costing a total of $108 million, according to a report released recently by the Interior Department's inspector general. USGS spokeswoman Anne-Berry Wade said Thursday the agency isn't sure why the employee falsified the results of chemical analyses but said it wasn't for personal gain or "any nefarious reason." A notice on a USGS website said the manipulation was done in part to correct calibration failures in the instrument being used, a mass spectrometer. The program made headlines two weeks ago when it said western Colorado contained 40 times more natural gas than previously thought, making it the second-largest gas formation in the country.