An audit by the Justice Department Inspector General Glenn Fine also found that more than half of the nearly 1,000 telecommunications bills reviewed by investigators were not paid on time, The Washington Post reported Thursday.
"Late payments have resulted in telecommunications carriers actually disconnecting phone lines established to deliver surveillance results to the FBI, resulting in lost evidence," Fine wrote in a seven-page summary of the audit's findings released Thursday.
In one FBI office alone, unpaid costs for wiretaps from one telephone company totaled $66,000, according to audit results, the newspaper reported.
FBI Assistant Director John Miller said in a statement that "there is widespread agreement that the current (agency) financial management system, first introduced in the 1980s, is inadequate."
The seven-page document issued Thursday was only a summary of the Justice Department inspector general's 87-page audit, which is classified and unavailable to the public.