CARACAS, Venezuela -- An American cargo ship captain has been freed without charge after being detained last week at a port in this South American country, a U.S. Embassy official said Monday.

The captain of the Ocean Atlas had been detained on Thursday after authorities found three assault rifles on the vessel. U.S. officials have said that the weapons were on the ship as a standard security measure to protect the vessel from attacks by pirates.

"Charges have been dropped, but there's still paperwork to be completed so the boat has not sailed away," Gregory Adams, a U.S. Embassy spokesman, told The Associated Press. "The captain is back on the ship with the crew."

Adams said that once paperwork is completed, the captain and the other 14 American crew members of the 120-meter (396-foot) vesse can set sail from the western port of Maracaibo.

The vessel's operator, Intermarine LLC, and Venezuelan Interior Ministry officials could not be reached for comment.

President Hugo Chavez said last month that Venezuelan authorities detained another U.S. citizen and were interrogating him because they suspected him of being a "mercenary." Chavez, a virulent critic of U.S. policies, said the American could be involved in a plot to destabilize the country if the opposition loses the Oct. 7 presidential election, but provided no details. The man remains in custody.

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