An eight-year-old lawsuit brought against America’s largesthealth insurer just got a big boost from the Trumpadministration.

On Friday lawyers for the Department of Justice joined a suitagainst UnitedHealthcare that accuses the insurancegiant of defrauding Medicare of hundreds of millions ofdollars.

“This is a very big development and sends a strong signal thatthe Trump administration is very serious when it comes to fightingfraud in the health care arena,” Patrick Burns, of TaxpayersAgainst Fraud in Washington, tells Kaiser Health News.

The suit was originally filed in 2009 by James Swoben, a formeremployee of SCAN Health Plan, which in 2012 agreed to pay $320million in a settlement with the Justice Department overallegations that it was fleecing Medicare Advantage by submittinginaccurate diagnosis codes that resulted in largerreimbursements.

Swoben and the federal government aren’t the only ones doggingUnitedHealth. One of its former executives launched a similar suitin 2011 accusing the company of defrauding taxpayers. DOJ is nowseeking to combine that suit with Swoben’s.

Investigations by journalists and government auditors in recentyears have uncovered evidence of significant Medicare fraud by bothinsurers and providers.

The Center for Public Integrity reported on numerous instancesof risk-score abuse by insurers in 2014 and alleged that insurershad “muzzled” investigation by Congress and regulators throughinfluence-peddling.

Agencies have been aware of massive overpayments for years, thereporting argued, but they were reluctant to go public with theirfindings due to embarrassment and industry pressure.

In 2013, for instance, the Centers for Medicare and Medicaid Servicesestimated that 9.5 percent of the payments made to Medicare Advantage plans were improper. But theagency balked at implementing a proposed regulation in thefollowing year to require insurers to report any improper paymentthey have received for a patient.

“The government isn’t in the best light when there’s that highan error rate,” health care attorney Thomas Hill said at the time. “They are reluctant to exposethat to the world.”

In 2015, a federal audit that was published appeared toconfirm the worst fears about Medicare Advantage. It concluded thatthe federal government had overpaid for half of all of the patientsenrolled in UnitedHealth’s Medicare Advantage plan.