DETROIT - Two sisters accused of falsifying health care claims to defraud the US government of millions of dollars were nabbed in Colombia and returned to the United States, authorities said on Tuesday.

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Caridad Guilarte, 54, and Clara Guilarte, 56, ran a clinic in Dearborn, Michigan, that billed about $9 million in claims for treatments patients never received, according to the US Department of Health and Human Services website.

The sisters collected more than $4 million from Medicare for drug therapies that were never provided, according to the HHS website.

After the FBI interviewed them, the two sisters fled, said Barbara McQuade, the US attorney for the Eastern District of Michigan at a press conference in Detroit.

The sisters were caught trying to enter Colombia through Venezuela and were using false travel documents.

McQuade, Attorney General Eric Holder and HHS Secretary Kathleen Sebelius were speaking on the sidelines of a conference in Detroit on preventing health care fraud.

Detroit is among the emerging "hot spots" for health care fraud because of its high unemployment and a large number of people addicted to drugs, McQuade told reporters.

Sebelius said the new US health reform law offers better access to data and predictive modeling that could help prevent fraud.

She said the government was "fortunate" to catch the Guilarte sisters, who were on the HHS department's most-wanted list. But she added, "their ability to move quickly out of the country gives us pause."