U.S. authorities have charged 107 people, including doctors and nurses, for trying to defraud the federal Medicare healthcare program for the elderly and disabled of about $452 million, the biggest Medicare fraud sweep to date, the Obama administration said on Wednesday.

At least 91 people were arrested in Miami; Houston; Baton Rouge, Louisiana, and four other cities on a variety of charges: from submitting false billing for home healthcare, mental health services, HIV infusions and physical therapy to money laundering and receiving kickbacks.

Justice Department and Health and Human Services Department officials were unable to say how much Medicare actually paid out, but a review of 34 complaints and indictments found that authorities were seeking to recover at least $59.5 million of allegedly ill-gotten gains.

“These fraud schemes were committed by people up and down the chain of healthcare providers – from doctors, nurses, and licensed clinical social workers, to office managers and patient recruiters,” said Lanny Breuer, assistant attorney general for the Justice Department’s criminal division.

Breuer said that it is the single largest Medicare billing fraud sweep by the Justice Department’s special task force in its five-year history. In September, the Obama administration charged 91 people in connection with a variety of schemes aimed at bilking Medicare out of $295 million.

The biggest cases were in Baton Rouge where seven people were arrested and charged with eight counts, including conspiracy and healthcare fraud for billing Medicare for some $225.6 million in unnecessary services and in some cases not providing services billed.

They ran and worked at two community mental health centers in Louisiana where they billed for more group therapy sessions than were provided, including recreational and education psychotherapy, according to court records.

Medicare paid out more than $37.9 million for the services to the two centers in Baton Rouge, identified as Shifa Community Mental Health Center and Serenity Center, according to the records.

In one case out of Miami, 10 people were charged with allegedly seeking $63 million in reimbursements from Medicare as some therapists altered their paperwork to try to justify services for patients who did not need them.

In another Florida case, one person was accused of receiving kickbacks to refer patients to a company that offered home health and physical therapy services, submitting $60 million in claims. Medicare reimbursed that group, NANY Home Health Inc, $40 million.

Last month, the three operators of NANY Home Health were sentenced to lengthy prison terms for their roles in the scheme and were ordered to pay $40 million in restitution.