U.S. Navy sailors who were freed Wednesday after being held by Iran were part of Riverine Squadron 1, based in San Diego, according to The Associated Press.
Iran detained the 10 sailors and their two small boats that drifted into Iranian waters Tuesday after experiencing mechanical problems. The sailors, nine men and one woman, were held overnight at an Iranian base on Farsi Island in the Persian Gulf, and were released on Wednesday morning local time.
The Revolutionary Guard's official website published images of the detained U.S. sailors before their release showing them sitting on the floor of a room. One was a woman with her hair covered by a brown cloth. The pictures also showed what appeared to be their two boats.
Iran's Revolutionary Guards (IRGC) said in a statement read on state TV Wednesday that the sailors had been released back into international waters after the U.S. issued an apology and clarifications that any incursion was "a mistake," NBC News reported.
"The Americans have undertaken not to repeat such mistakes," the statement said. "The captured marines were released in international waters under the supervision of the IRGC Navy."
The U.S. Navy confirmed that the sailors had been "safely returned" after departing Iran's Farsi Island at 3:43 a.m. ET aboard the riverine vessels they had been operating when the incident occurred.
Iran accused the sailors of trespassing but American officials said Tuesday Tehran had assured them that the crew and vessels would be returned safely and promptly. Officials said Tuesday they believe the U.S. had spoken to one of the crew, and all 10 were fine and uninjured.
The squadron's sailors were deployed to the U.S. Navy's 5th Fleet in Bahrain. When the U.S. lost contact with the boats, ships attached to the USS Harry S Truman aircraft carrier strike group began searching the area, along with aircraft flying off the Truman.
Pentagon spokesman Peter Cook told the AP that the Riverine boats were moving between Kuwait and Bahrain when the U.S. lost contact with them.
U.S. officials said that the incident happened near Farsi Island in the middle of the Gulf. They said some type of mechanical trouble with one of the boats caused them to drift into Iranian territorial waters near the island, and they were picked up by Iran.
The semi-official Iranian news agency, FARS, said the Iranian Revolutionary Guard's navy has detained 10 foreign forces, believed to be Americans, and said the sailors were trespassing in Iranian waters.
"We have been in contact with Iran and have received assurances that the crew and the vessels will be returned promptly," Cook said.
The incident came amid heightened tensions with Iran, and only hours before President Barack Obama was set to deliver his final State of the Union address to Congress and the public. It set off a dramatic series of calls and meetings as U.S. officials tried to determine the exact status of the crew and reach out to Iranian leaders.
Secretary of State John Kerry, who forged a personal relationship with Iranian Foreign Minister Mohammed Javad Zarif through three years of nuclear negotiations, called Zarif immediately on learning of the incident, according to a senior U.S. official. Kerry "personally engaged with Zarif on this issue to try to get to this outcome," the official said.
Kerry learned of the incident around 12:30 p.m. EST as he and Defense Secretary Ash Carter were meeting their Filipino counterparts at the State Department, the official said.
Officials said the sailors were part of Riverine Squadron 1 based in San Diego and were deployed to the U.S. Navy's 5th Fleet in Bahrain. When the U.S. lost contact with the boats, ships attached to the USS Harry S Truman aircraft carrier strike group began searching the area, along with aircraft flying off the Truman.
Officials said a radio signal from one of the boats showed that they were on Farsi Island, setting off efforts to contact the Iranians. The Riverine boats were not part of the carrier strike group, and were on a training mission as they traveled between Kuwait and Bahrain, officials said.
The Riverine boats are not considered high-tech and don't contain any sensitive equipment, so there were no concerns about the Iranians gaining access to the crafts.
The officials were not authorized to discuss the sensitive incident publicly so spoke on condition of anonymity.
Republican lawmakers seized on the incident as further evidence that Iran is not to be trusted. The House was scheduled to vote Wednesday on GOP-backed legislation that would give Congress greater oversight of the landmark Iran nuclear agreement, which Republicans have derided as a victory for Tehran.
Sen. Kelly Ayotte, R-N.H., said it was "unthinkable that the administration would lift sanctions and permit Iran to receive billions of dollars in sanctions relief under the nuclear agreement, even as the regime brazenly violates its international obligations and rushes to develop the ballistic missile capability to deliver a potential nuclear weapon to the United States."
The incident came on the heels of an incident in late December when Iran launched a rocket test near U.S. warships and boats passing through the Strait of Hormuz.
Meanwhile, Iran was expected to satisfy the terms of last summer's nuclear deal in just days. Once the U.N. nuclear agency confirms Iran's actions to roll back its program, the United States and other Western powers are obliged to suspend wide-ranging oil, trade and financial sanctions on Tehran. Kerry recently said the deal's implementation was "days away."
NBC 7 San Diego's Samantha Tatro contributed to this report