Investigators charged with conducting background checks of U.S. national-security workers have falsified records and aren’t receiving adequate oversight, Bloomberg reports.

According to an inspector general’s testimony, one worker fabricated 1,600 credit checks before it was discovered that her own background investigation had been falsified.

Eighteen investigators, including contract and government employees have been convicted of falsifying reports since 2006, and Patrick McFarland, inspector general of the U.S. Office of Personnel Management, says the office lacks the resources to clear a backlog of 36 additional cases.

The Office of Personnel Management is responsible for some 90 percent of the background investigations of U.S. government employees and contractors. The Pentagon and Department of Homeland Security are its biggest users. The personnel office conducts more than 2 million investigations each year, Bloomberg reports. The office also vets applicants for federal agency jobs and applicants for security clearances.