A U.S. government subcontractor was put in a high-security Cuban prison instead of a common jail after his arrest in Havana as he was about to take a flight home, U.S. congressional officials said Monday.

The type of prison signaled that Cuban authorities are taking seriously the case of the U.S. citizen, reportedly detained for handing out laptops, cellphones and other communications equipment as part of a U.S. government program to support democracy in Cuba.

Cuba has long regarded U.S. pro-democracy activities on the island as an effort to subvert its government, and in 2003 sentenced 75 dissidents to long prison terms on charges of receiving aid from Washington. It also has detained several U.S. citizens over the decades on spying charges.

Florida Sen. Bill Nelson wrote a private letter to Secretary of State Hillary Clinton Thursday noting that the man was "being held without charge in a high security prison" and urging her to "use all available means to secure this citizen's release."

Earlier that day, State Department officials had briefed the staffs of Nelson and other members of Congress who keep an eye on Cuba issues, and told them the American was detained at the Havana airport when he turned up for his flight home, a congressional aide said.

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