Iran is holding 10 American Navy sailors and their two small Navy boats after the boats had mechanical problems and drifted into Iranian waters, The Associated Press (AP) reported Tuesday.

American officials said, however, they have received assurances from Tehran that they will be returned safely and promptly.

Pentagon spokesman Peter Cook told AP that the riverine boats were moving between Kuwait and Bahrain when the U.S. lost contact with them.

American officials said that the incident happened near Farsi Island, situated in the Persian Gulf. They said that some type of mechanical trouble with one of the boats caused them to run aground and they were picked up by Iran.

According to AP, Iran’s semiofficial 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.

Tuesday’s incident follows an incident in late December when the Iranian navy test fired several rockets near three Western warships, including the USS Harry S. Truman aircraft carrier, near the Strait of Hormuz.

Iran later denied that its navy launched rockets  next to American warships, but footage later released by the American Navy proved that the incident did indeed take place.