The number of Cuban migrants arriving in the United States from Cuba has declined partly because hundreds of smugglers are now in prison as a result of a federal crackdown, according to immigration officials.

At least 546 migrant smugglers have been criminally charged in more than 300 federal indictments in South Florida since 2006 and most of these defendants have been convicted and are now serving prison sentences, said Kevin Crowley of the U.S. Immigration and Customs Enforcement homeland security investigations.

``The amount of people we have put in prison plus other factors have contributed to the decline in numbers,'' said Crowley, assistant special agent in charge in Miami. ``There are people incarcerated right now who cannot smuggle.''

Recent figures released by several federal agencies showed that the number of Cubans interdicted by the Coast Guard or arriving from Mexico was way down. The figures cover undocumented Cuban migrants, not the estimated 20,000 annual immigrant visas issued by the U.S. Interests Section in Havana.

The figures showed that fewer than 7,000 undocumented Cubans were interdicted or arrived at the border during the 12-month period that ended Sept. 30 -- a huge drop from the peak of almost 20,000 in 2007.

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