Federal investigators said Monday that they are ending their search for the voyage data recorder of a cargo ship that sank in the Atlantic during a hurricane, but remained hopeful that they could determine what happened to the ship without it.

"Over the years we've completed many investigations without the aid of recorders and other investigative tools," National Transportation Safety Board Chairman Christopher Hart said in a statement.

Hart said investigators are disappointed the El Faro's "black box" was not found, but hopeful they can still find enough evidence to determine a probable cause of its sinking.

The 790-foot freighter sank on Oct. 1 after it lost engine power and was disabled in the path of a Category 4 hurricane. The ship, with 33 crew members on board, was on its way from Jacksonville to Puerto Rico. No survivors were found.

NTSB officials said recently that searchers had located the ship and its bridge, which had separated, in 15,000 feet of water.

Still, a Navy submarine searching the area could not find the ship's mast, where the recorder was mounted, Hart said.

The data recorder charts the date, time and speed of a marine vessel, and also records conversations on the bridge that could include key decision-making between captain and crew.

Recovering equipment at such depth is difficult, but has been done in other cases.

Crews found the black boxes of an Air France jetliner that crashed into the Atlantic Ocean on June 1, 2009 on a flight from Rio de Janeiro to Paris. The boxes were found in about 12,800 feet of water, but it took nearly two years after the wreckage was identified to find them. The boxes did prove instrumental in determining that pilot error contributed to the crash.

Crews also retrieved the black box of a South African Airways airplane that plummeted into the Indian Ocean in 1987. That box was recovered from a depth of more than 15,000 feet, but did not help investigators identify a definitive cause of the crash.

Since the El Faro's sinking, a number of lawsuits have been filed by families accusing the ship's owner, Tote Marine, and its captain, Michael Davidson, of wrongful death and negligence. They argue the ship should never have tried to outrun a hurricane, and that the decision to do so was motivated by money.

Tote Marine has filed its own suit seeking to limit or release its liability, and company officials have claimed the El Faro was maintained properly and in good condition.

The NTSB still has a lot of investigative avenues to help determine what happened, even without the data recorder, said Marjorie Cooke, a marine safety expert with Robson Forensic and former director of the NTSB's office of marine safety.

For example, images from the Navy's remotely operated vehicle, or ROV, which explored the wreckage will provide important information about the ship's shape in those final hours, she said.

Also, there should be a lot of communications between Tote and the captain, and emails from crew to family from the ship to help piece together what occurred, she said.

Voice data recorders were only required on vessels fairly recently, Cooke said, but many sinking-ship cases were solved prior to their regular use by other means, Cooke said.

"There's an awful lot of information from the classification society, the ship owner and the Coast Guard in regards to the vessel's condition," she said.