With billions in taxpayer dollars at stake, the Obama administration has taken a “passive” approach to identifying potential fraud involving the president’s health care law, nonpartisan congressional investigators say in a report released Wednesday.

While the Government Accountability Office stopped short of alleging widespread cheating in President Barack Obama’s signature program, investigators found that the administration has struggled to resolve eligibility questions affecting millions of initial applications and hundreds of thousands of consumers who were actually approved for benefits.

The agency administering the health law — the Centers for Medicaid and Medicare Services — “has assumed a passive approach to identifying and preventing fraud,” the GAO report said. In a formal written response, the administration agreed with eight GAO recommendations while maintaining that it applies “best practices” to fraud control.