0238 GMT June 18, 2019
Ten US sailors, who were aboard two patrol craft, were detained by the Islamic Revolution Guards Corps (IRGC) on Jan. 12 when they inadvertently entered Iranian territorial waters. They were released the next day after being held for about 15 hours, Reuters reported.
The US military said the Americans were intercepted after the diesel engine in one of their boats developed a mechanical problem.
The official, speaking on condition of anonymity, said the investigation also found the incident was caused by communication failures and not enough oversight and training.
Findings of the five-month-long investigation will be presented by Admiral John Richardson, the chief of US Naval Operations, at a briefing in the Pentagon on June 30 where he will give more details on the incident, the official said.
If any punishments will have been decided by then, they will be announced by Richardson, the official added.
"The investigation is complete, and is being referred to appropriate commands for adjudication," said US Navy spokesman Commander Mike Kafka.
In May, the US Navy said it had fired the commander of the 10 American sailors. At the time, a Navy statement said that it had lost confidence in Commander Eric Rasch, who was the executive officer of the coastal riverine squadron.