Ten sailors and two boats were taken into Iranian custody Tuesday after their patrol boats drifted into Iranian-claimed waters, with Iranian officials suggesting they could be released as soon as Wednesday.

The riverine sailors, riverines, are believed to have drifted into Iranian territory after having mechanical issues with their boats. The defense officials said Secretary of State John Kerry got was immediately involved and Iran has agreed to turn the sailors and vessels over, though they have not been turned over as of 4 p.m., Eastern Standard Time.

Fleet officials lost contact with the riverine boats in the vicinity of Farsi Island, an Iranian island in the north Persian Arabian Gulf. A U.S. official said it’s believed they drifted into the 12-mile zone near the island while in transit. The island is believed to be a base for the Iranian Revolutionary Guard Corps.

The U.S. detainees, nine men and a woman, were held overnight at Farsi Island and were expected to be transferred to a U.S. ship in the region Wednesday, the Associated Press reported.

"Investigation shows that the entry of American sailors into Iran's territorial waters was due to mechanical problems in their navigation system," Gen. Ali Fadavi, Navy chief of Iran's elite powerful Revolutionary Guard, was quoted as saying on Iranian state TV.

It is unclear whether the Iranian forces boarded the U.S. boats or confronted the sailors. U.S. officials said Tuesday that they expected the sailors to be released quickly by Iran.

"Earlier today, noonish eEast cCoast, we lost contact with two small U.S. naval craft en route from Kuwait to Bahrain," said a defense official, who, like others, asked for anonymity to discuss ongoing negotiations. "We subsequently have been in communication with Iranian authorities, who have informed us of the safety and well-being of our personnel. We have received assurances the sailors will promptly be allowed to continue their journey."

"We found out that the Iranians may actually have them so we initiated state-to-state contact," said another defense official.

The Iranians have assured the U.S. the sailors will be released unharmed soon, a senior defense official said.

"We subsequently have been in communication with Iranian authorities, who have informed us of the safety and well-being of our personnel," the unnamed official said in a Tuesday statement. "We have received assurances the sailors will promptly be allowed to continue their journey."

Officials at 5th Fleet headquarters in Bahrain did not immediately respond to requests for comment. An official at U.S. Central Command referred questions to the Office of the Secretary of Defense.

Pentagon spokesman Peter Cook told The Associated Press that the boats were moving between Kuwait and Bahrain when the U.S. lost contact with them. The situation began to unfold during the evening in at about noon eastern time, evening in the Persian Gulf, according to a defense official. The Truman Carrier Strike Group launched a search-and-rescue effort and is still in the vicinity.  

A skeletal look at the Navy's new Riverine Command Boat. The ultra-fast vessel was built in Sweden, which prevented the Navy from buying one until now.

Photo Credit: SAFE Boats

The New York Times reported that Iran’s Fars news agency said the riverine boats traveled more than mile into Iranian terroritial territorial waters and that the Revolutionary Guard Corps seized some GPS gear to show the vessels had been "snooping." 

A Defense spokeswoman identified the American vessels as riverine command boats. These 49-foot-long vessels feature an aircraft-like cockpit and a reinforced hull that can drive onto a rocky beach to offload troops. They're a cross between a boat and a Stryker armored combat vehicle, according to a 2007 Navy Times profile of the boats.

With Rolls-Royce jets that propels it up to 43 knots, these $2.8 million boats are the flagships of the brown water Navy. They are designed for rivers and coastal waterways, with a three foot draft. The fast-attack craft host sensitive communications gear to act as a floating command post for riverine forces and can be outfitted for different missions.

These command boats can carry up to 20 troops and be armed with six crew-served machine guns, or alternately serve as an floating ambulance.

"Earlier today, we lost contact with two small U.S. naval craft en route from Kuwait to Bahrain," Cook said in a Tuesday statement. "We subsequently have been in communication with Iranian authorities, who have informed us of the safety and well-being of our personnel. We have received assurances the sailors will promptly be allowed to continue their journey."

Cook says, "We have been in contact with Iran and have received assurances that the crew and the vessels will be returned promptly."

The situation is reminiscent of a 2007 incident when 15 British sailors were captured by the Iranian Revolutionary Guard and held for two weeks.

Video: U.S. Navy Riverine Command Boat

File video provided by the Defense Department shows a Navy Riverine Command Boat, the same type of vessels Iran seized Jan. 12 after two of the boats experienced mechanical issues in teh Persian Gulf.

The Iranian seizure is the latest flare-up in an increasingly tense relationship. Two weeks ago, U.S. officials blamed patrol boats with the Iranian Revolutionary Guard Corps for firing rockets in the vicinity of the Truman Carrier Strike Group, which was then passing through the Strait of Hormuz. Those officials labeled it a "dangerous" and "unprofessional" stunt.

Some experts have cautioned that Iran's elite paramilitary forces are likely to continue to seek provocations with the West, even as Iran enters into a nuclear agreement.

The Associated Press and Staff writer Meghann Myers contributed to this report.

Staff writer David Larter contributed to this report.

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