The U.S. Navy on Monday released nine of the 16 suspected pirates it holds, saying there was a lack of evidence to prosecute the men, according to the Navy.

The nine men had been held on a Navy-contracted cargo ship since being detained in a Feb. 12 incident in which the Indian-flagged Motor Vessel Premdivya sent a distress call stating the ship had been fired upon at night by a small skiff.

The nine men have been turned over to the Puntland Coast Guard. Puntland is a semi-autonomous region of Somalia and self-proclaimed Somali state that includes the point of the Horn of Africa.

The nine men had been stopped in the general vicinity of the Indian ship after the reported attack and possessed weapons and equipment commonly used in pirate attacks, according to Monday’s news release from U.S. Naval Forces Central Command, which is based in Bahrain.

"While maintaining custody of the Somali nationals, the U.S. Navy evaluated the situation and determined there was inconclusive evidence to support their prosecution," the release read. "As a result, the nine Somali nationals were transferred to the Puntland Coast Guard to facilitate their safe return to shore. While aboard U.S. Navy ships, the Somali nationals were treated humanely."

The remaining seven suspected pirates, also taken into custody in mid-February, are still being held on the USNS Lewis and Clark, a civilian ship usually used to haul cargo and ammunition. The Lewis and Clark has been reconfigured to hold as many as 26 suspected pirates. It also serves as a staging platform for the U.S.-led Combined Task Force 151 and is able to launch either of the SH-60 Navy helicopters now assigned to the ship to combat piracy in the region.

A January agreement between the U.S. State Department and the Kenyan government lets U.S. military and coalition nations capture suspected pirates and turn them over to Kenya for prosecution.

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