The search for the Malaysian airliner that vanished almost two years ago has found a second 19th century shipwreck deep in the Indian Ocean off the west Australian coast.

A sonar search for the wreckage of Malaysia Airlines Flight 370 found what appeared to be a man-made object on December 19, the Australian Transport Safety Bureau said.

A follow-up investigation using an underwater drone captured high-resolution sonar images on January 2 that confirmed that the find was a shipwreck, said the bureau, which is running the search for the Boeing 777 which vanished on March 8 2014.

The Shipwreck Galleries of the Western Australian Museum conducted a preliminary review of the images and advised that the wreck was likely to be a steel or iron ship dating from the turn of the 19th century, the bureau said.

The wreck was found under water 12,100 feet deep, 1,600 miles south-west of the Australian port of Fremantle where the three search vessels are based, the bureau said.

The sea hunt similarly found what appeared to be a man-made object in March last year 12,800 feet deep. But it was not until May that a closer look confirmed that it was not plane wreckage but the wreck of a cargo ship built in the mid-to-late 19th century.

Hundreds of such ships were lost during voyages across the Indian Ocean. Neither ship is likely to be identified because of the cost of mounting closer examinations.

Flight 370 is thought to have crashed in the Indian Ocean with 239 passengers and crew on board more than 1,100 miles south-west of Australia after mysteriously flying off course during a flight from Kuala Lumpur to Beijing.

Searchers have been combing a 46,000-square-mile part of the Indian Ocean since late 2014. A wing flap found in July on the other side of the Indian Ocean when it washed up on Reunion Island is the only debris recovered.

More than 30,000 square miles of the seafloor have been scoured so far, and the search is scheduled to be wound up by the middle of the year if nothing else of Flight 370 is found.