Story highlights NTSB arrives on site and says it will "leave no stone unturned in our investigation"

El Faro was carrying a crew of 28 Americans and five Polish nationals

The U.S. Coast Guard has concluded that the ship sank; officials are searching for survivors

(CNN) The owners of a cargo ship presumed to have sunk insist that the captain of El Faro had a "sound plan" to avoid Hurricane Joaquin, but that the ship's main propulsion failed, stranding the crew in the path of the storm.

The unidentified captain had real-time weather information when he left the port in Jacksonville and reported favorable conditions at the outset, Tote Services President Phil Greene told reporters.

Given the weather system, the captain's "plan was a sound plan that would have enabled him to clearly pass around the storm with a margin of comfort that was adequate in his professional opinion," Greene said on Monday night.

Still, the question that came up over and over again at the news conference at which Tote Incorporated President and CEO Anthony Chiarello, Tote Maritime Puerto Rico President Tim Nolan and Greene attended was a version of this: Knowing that a potential hurricane was brewing, why was El Faro allowed to go ahead with its scheduled route?

The U.S. Coast Guard has concluded that the ship, which was carrying 28 Americans and five Polish nationals, sank last week. It was headed from Jacksonville, Florida, to San Juan, Puerto Rico, when it disappeared near the Bahamas.

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