A nationwide law enforcement crackdown has charged 91 people — including doctors and other medical professionals — with participating in Medicare fraud schemes involving $295 million in false billing.

Attorney General Eric Holder and Health and Human Services Secretary Kathleen Sebelius said Wednesday that 70 people were charged in indictments unsealed Tuesday and Wednesday and 21 others were charged earlier, beginning Aug. 24. Charges were filed in Baton Rouge, La.; Brooklyn, N.Y.; Chicago, Dallas, Detroit, Houston; Los Angeles and Miami.

At a news conference, the attorney general said that those arrested are "jeopardizing the integrity of our health care system." Sebelius called the law enforcement initiative "a powerful warning to those who would try to defraud taxpayers and Medicare beneficiaries.

Eleven of the people charged were doctors, three were nurses and 10 were licensed health professionals.

Over half the defendants — 46 — and $160 million of the total in phony claims announced Wednesday came from South Florida, still leading the nation in Medicare fraud.

In Miami, U.S. Attorney Wifredo Ferrer said investigators noticed a new twist in which people who already were receiving Medicare disability checks were recruited with promises they could live in a halfway house in South Florida — as long as they agreed to receive mental health services they did not need. Many were addicted to drugs or alcohol, and some were homeless, and Ferrer said they would be threatened with eviction if they did not participate in the fraud scheme.

"They were already in the system. They were lured in by the promise of having housing. It was, 'Come and have a fresh start in Miami,'" Ferrer said.

That particular scheme and other frauds, operated out of an entity called Biscayne Milieu, accounted for $50 million of the fraudulent Medicare claims, prosecutors said. It provided no legitimate services.

"It was a complete fraud," Ferrer said.

In Houston, two people were charged with fraud schemes involving $62 million in false claims for home health care and medical equipment. One defendant allegedly sold beneficiary information to 100 Houston-area home health care agencies. The home agencies used the information to bill Medicare for services that were unnecessary or never provided.

In Baton Rouge, La., a doctor, nurse and five other co-conspirators were charged with billing Medicare more than $19 million for skilled nursing and other home health services that were not necessary or never provided.