The US navy has found wreckage it believes to be from the doomed freighter El Faro which sank during Hurricane Joaquin a month ago, the National Transportation Safety Board said Saturday.

El Faro was en route from Florida to Puerto Rico with a cargo of containers and automobiles on October 1 when it was caught in a ferocious storm in the Bahamas.

The entire crew of 33 is believed to have perished.

Crew from the US Navy fleet ocean tug boat, the Apache, found a vessel Saturday "at a depth of about 15,000 feet in the vicinity", an NTSB statement said.

"Sophisticated sonar equipment towed from Apache first detected what are believed to be images of the vessel using Orion, a side-scanning sonar system," it said.

To confirm the find "specialists on Apache will use CURV 21, a deep ocean remotely operated vehicle, to survey and confirm the identity of the wreckage," it added.

That work could begin as soon as Sunday, the NTSB said.

The operations are expected to take up to 15 days to complete but could take longer depending on weather conditions.