Testimony at a U.S. Coast Guard investigative hearing revealed that a cargo ship that sank after losing propulsion in a hurricane could have suffered a catastrophic boiler explosion.

Lou O'Donnell, assistant chief surveyor with the American Bureau of Shipping, told the panel on Friday that the cargo ship's hot boiler could have exploded if it was exposed to cold water entering the sinking ship.

The El Faro sank on Oct. 1, 2015, while traveling between Jacksonville, Florida, and Puerto Rico. All 33 aboard died.

Coast Guard Capt. Jason Neubauer said images of the ship's wreckage 15,000-feet-deep in the Atlantic show evidence of damage that could possibly be from an explosion.

O'Donnell said he had reviewed the photos, but could not say for sure if an explosion had occurred.