Updated

More than 100 defendants are being charged in seven cities with Medicare fraud in a nationwide crackdown.

Federal authorities said the unrelated scams allegedly bilked the taxpayer-funded program of more than $450 million — the highest dollar amount in a single Medicare bust in U.S. history.

Health and Human Services Secretary Kathleen Sebelius and Attorney General Eric Holder held a press conference in Washington to announce the arrests. Their agencies partnered in 2009 to increase enforcement by allocating more money and staff and creating strike forces in fraud hot spots.

On Tuesday, hundreds of federal agents fanned out around the country, raiding businesses, seizing documents and arresting suspects in Miami, Los Angeles, Houston, Detroit, Chicago, Tampa, Fla., and Baton Rouge, La.