The Pentagon has backed off claims that a mechanical failure contributed to U.S. sailors drifting into Iranian waters and touching off a diplomatic incident earlier this week, with Defense Secretary Ash Carter now saying a “navigation error” was to blame.

"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 said in a television interview with Univision at U.S. Southern Command in Miami. 

"So that seems to be the original cause of this, according to the interviews that we have done," Carter added.

On Tuesday, 10 U.S. sailors were temporarily detained by Iran after their two Riverine boats entered Iranian waters near Farsi Island in the Persian Gulf. The sailors were released after State Department intervention, though videos of Iranians commandeering the boats and later getting an apology from one of the sailors have since caused headaches for Washington.

Initial indications from U.S. officials were that a mechanical failure was to blame.

Yet both boats were able to exit the area once the sailors were released, raising questions about that explanation.

Late Wednesday, Fox News was told that a mechanical failure indeed had been ruled out as the cause for the two U.S. Navy vessels drifting into the hands of the Iranians. 

What remains a mystery is the timeline of events leading up to the detention by Iran’s Revolutionary Guard Corps forces on Tuesday. 

Fox News is told only a few senior officers are read into the details of what exactly happened.

“This administration is putting diplomatic relations above transparency,” one defense official told Fox News.

The 10 Navy sailors were released at 3:43 a.m. ET early Wednesday morning. They are currently in Qatar.

Lucas Tomlinson is the Pentagon and State Department producer for Fox News Channel. You can follow him on Twitter: @LucasFoxNews