Contractors paid tens of millions of taxpayer dollars to detect fraudulent Medicare claims are using inaccurate and inconsistent data that makes it extremely difficult to catch bogus bills submitted by crooks, according to an inspector general's report released Monday. Medicare's contractor system has morphed into a complicated labyrinth, with one set of contractors paying claims and another combing through those claims in an effort to stop an estimated $60 billion a year in fraud. The U.S. Department of Health and Human Services inspector general's report ? obtained by The Associated Press before its official release ? found repeated problems among the fraud contractors over a decade and systemic failures by federal health officials to adequately supervise them. Investigators found that health officials did not consistently evaluate key measures such as how many investigations were initiated by contractors. Investigators examined two contractors in charge of fraud hot spots in Florida and Texas during a nine-month period.