Preview: Lost in the Bermuda Triangle

The El Faro lies nearly three miles beneath the Atlantic in the infamous Bermuda Triangle after sinking in Hurricane Joaquin last October, taking the lives of 33 men and women who were aboard. As the National Transportation Safety Board conducts its investigation into the worst U.S. maritime disaster in 35 years, it allowed 60 Minutes to report on its activities and to broadcast footage of the sunken cargo ship -- the first video of it to be seen in public. Scott Pelley reports from aboard the U.S. Navy's salvage and diving vessel Apache for this story on the next edition of 60 Minutes, Sunday, Jan. 3 at 7:30 p.m. ET and 7 p.m. PT.

Tom Roth-Roffy, the NTSB's lead investigator on the El Faro case, is looking at many factors to determine the cause of the sinking. "This is the most difficult and complex investigation I have ever worked on in my 17 years with the National Transportation Safety Board," says Roth-Roffy. Despite many hurdles, including the great depth at which the wreck lies, Roth-Roffy is confident he will be able to determine a cause.

"We've experienced this sort of challenge before on other investigations and we're hopeful that we will be able to determine the cause of the sinking," Roth-Roffy tells Pelley.

A major challenge for Roth-Roffy is the absence of the ship's Voyage Data Recorder (VDR), which would give him and others access to the conversations on El Faro's bridge that could offer more clues. The device went missing when the vessel's top two decks -- including the bridge, where the captain would have been -- were shorn off.

60 Minutes will show footage of the sunken vessel for the first time taken by cameras attached to the Apache's cable-controlled underwater recovery vehicle. The images they recorded disturbed Roth-Roffy. "We were looking, of course, for the bridge and the Voyage Data Recorder...we got up to that level and to see just openness, is extremely moving and difficult...it was a very big surprise," says Roth-Roffy of the realization that some of the crew may have been swept away with the two decks.

Pelley also speaks to family members of some of those lost at sea and to the chairman of the NTSB, Christopher Hart. He says it may take up to a year to answer all the questions surrounding the sinking of the El Faro.