The hunt for missing Malaysia Airlines Flight MH370 has discovered an uncharted shipwreck in the southern Indian Ocean, BBC News reports.

Peter Foley, who heads the search team, said the find was "fascinating... But it's not what we're looking for".

However, he said the find showed that if the flight was in the search area, it would be discovered. MH370 vanished last year en route from Kuala Lumpur to Beijing with 239 people on board.

No trace has been found and there is no explanation for its disappearance.

Search teams have been focusing on a 60,000 sq km (23,000 sq mile) area off the coast of Western Australia, where it is believed to have crashed.

The shipwreck was discovered when sonar equipment detected a cluster of objects almost 4km (2.5 miles) under the sea.

Officials suspected it was not the missing jet, but sent down an underwater camera to investigate.

"Obviously, we're disappointed that it wasn't the aircraft," said Foley, from the Australian Transport Safety Bureau (ATSB).

"And this event has really demonstrated that the systems, people and the equipment involved in the search are working well. It's shown that if there's a debris field in the search area, we'll find it."

The wreck is of a 19th Century cargo ship, said Michael McCarthy, a senior maritime archaeologist at the West Australian Maritime Museum.

"We've got quite a lot of stories about ships that sank in the Indian Ocean mid-voyage and you would be struggling to tell which is which unless you had a complete catalogue of all the ones lost," he told the AP.

Last month, officials said the search area would be doubled if nothing was found in the current search zone.