Congressional investigators say the government has failed to inspect thousands of oil and gas wells it considers potentially high risks for water contamination and other environmental damage.
The report highlights substantial gaps in oversight by the agency that manages oil and gas development on federal and Indian lands.
The Associated Press obtained the Government Accountability Office audit ahead of its public release.
Investigators say weak control by the Interior Department's Bureau of Land Management resulted from policies based on outdated science and from incomplete monitoring data.
The findings come amid an energy boom in the country and the increasing use of hydraulic fracturing, or fracking.
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