MIAMI – Attorney General Eric Holder has announced "the largest federal healthcare fraud takedown in the nation's history," involving 94 people in four cities, charged in alleged schemes to submit more than $251 million in false Medicare claims.

At a Medicare Fraud Strike Force press conference Friday in Miami, Holder said those charged include physicians, medical assistants and healthcare company owners and executives. The defendants allegedly participated in schemes to submit claims to Medicare for treatments that were not medically necessary and often never provided, he said.

Holder was flanked by Health and Human Services Secretary Kathleen Sebelius, Special Agent John Gillies of the FBI's Miami Field Office, HHS Inspector General Daniel Levinson and the U.S. Attorney for the Southern District of Florida Willy Ferrer when he made the announcement.

Twenty-four Miami defendants have been charged for their alleged involvement in fraud schemes totaling approximately $103 million, while additional arrests were made in Baton Rouge, Brooklyn and Detroit, Holder said.

According to Holder, the sting operation was led by the Medicare Fraud Strike Force, a joint initiative between the Departments of Justice and HHS. More than 360 law enforcement agents from the FBI, the HHS' Office of Inspector General, multiple Medicaid Fraud Control Units and other federal, state and local law enforcement agencies participated.

Holder said the arrests "prove the federal government is working aggressively and collaboratively to pursue healthcare criminals around the country and to bring these offenders to justice." He said they mark "a critical step forward in combating and deterring such illegal activity," and that "our work is far from over."

Law enforcement agents are still issuing search warrants in connection with ongoing healthcare fraud investigations, Holder said. "We will continue to follow the evidence in these cases wherever it leads us," he said.

Since March 2007, when the first phase of the Strike Force was launched in south Florida, the initiative has resulted in the indictments of more than 810 organizations and individuals, including those charged Friday.

"By improperly billing Medicare for more than $1.85 billion, these criminals have siphoned resources from the most vulnerable among us," Holder said.

"With today's arrests, we're putting would-be criminals on notice: Healthcare fraud is no longer a safe bet. It's no longer easy money. If you choose to engage in healthcare fraud, you will be found, you will be stopped and you will be brought to justice," he said.