The U.S. Justice Department has intervened in a whistleblower case against one of the country’s largest hospital chains, alleging that three of its Georgia hospitals paid kickbacks for more than a decade to a chain of metro Atlanta prenatal clinics in return for patient referrals.

In a filing late Tuesday, the DOJ sought unspecified financial restitution for Medicaid claims made from 2000 through 2013 that were filed as a result of the alleged scheme. Federal prosecutors have also asked the court to award treble damages and other civil penalties under the federal False Claims Act.