The U.S. Navy alerted Iran that it was deploying one of its vessels as part of a search and rescue effort for 10 sailors who were off course and allegedly inside Iranian waters, CNN learned from an unnamed U.S. defense official with direct knowledge of the latest information about the incident.

Secretary of Defense Ash Carter said Thursday that a “navigational error” accidentally led the 10 American sailors and their two Riverine Command Boats (RCB) into Iranian waters.

“Commanders in the U.S. Navy’s Fifth Fleet in the region became alarmed when the sailors missed a planned check-in call on their radios,” reports CNN. “At that point, commanders checked the GPS system tied to the boats and realized they were off course and inside Iranian waters.”

“A search-and-rescue effort was launched — including sending a U.S. Navy vessel inside Iranians waters due to concern the sailors could have been overboard and in the water,” it adds.

CNN quoted the official as saying that “the U.S. Navy informed Iranian military vessels in the area they were coming in for a search-and-rescue.”

Nevertheless, the Iranian Revolutionary Guards Corps (IRGC) detained the 10 sailors and seized their two boats Tuesday, within three miles of the IRGC naval base in Iran’s Farsi Island, described as an “extremely sensitive” facility by CNN.

“It then became known the 10 sailors had been taken ashore and diplomatic efforts to get them out quickly kicked in,” notes CNN.

Iran has since released the sailors and their two boats. The Navy believes the Iranians did not remove any gear or weapons from the boats, reportedly said the anonymous official.

In an interview with Spanish-language broadcaster Univision in Miami, Secretary of Defense Ash Carter said that a “navigational error” led the American sailors into Iranian waters.

“The information that they have given us, and through their commanders is that they did stray accidentally into Iranian waters due to a navigation error,” Carter told Univision on Thursday. “So that seems to be the original cause of this, according to the interviews that we have done.”

Reuters, citing the Univision interview, quotes Carter as saying that “the sailors apparently did not radio in to tell U.S. commanders they were off-course before encountering the Iranians.”

“They did not report this navigational error at the time. It may be that they were trying to sort it out at the time they encountered the Iranian boats and discovered they were inside of the territorial waters of Iran,” said Carter, who denied that the sailors were on a covert mission.

“They were simply transiting from one place to another,” he said. The U.S. Navy boats were reportedly en route to Bahrain from Kuwait.

CNN learned from the U.S. defense official that the “the boats had drifted off course, but one was also suffering engine trouble, making it impossible for the Americans to rapidly back off and return to international waters when they were approached by armed Iranian naval boats.”

It remains uncertain whether the American sailors defended themselves before they were captured, a Pentagon spokesman told Breitbart News, saying the Department of Defense was waiting to debrief the sailors about chronology and the events that led up to their detention.

“I will never surrender of my own free will. If in command, I will never surrender the members of my command while they still have the means to resist,” dictates Article 2 of the U.S. Navy Code of Conduct.

“If I am captured, I will continue to resist by all mens available. I will make every effort to escape and aid others to escape. I will accept neither parole nor special favors from the enemy,” adds Article 3.

The debriefing process has begun, according to the official who spoke to CNN on condition of anonymity.

He said, “The U.S. Navy has initial statements from the sailors, but is now conducting a full debrief, so additional information may come to light.”