Australia will step up search efforts in an area they believe holds the best hope of finding a missing Malaysia Airlines jet, whose disappearance last year sparked one of the greatest mysteries in aviation history, officials said on Thursday.

An Australian-led underwater search, the most expensive ever conducted, has so far found no trace of Malaysia Airlines Flight MH370, which went missing with 239 passengers and crew during a flight from Kuala Lumpur to Beijing in March 2014.

The number of vessels searching for the jet would be doubled to four, Australian Deputy Prime Minister Warren Truss said. One of the vessels would be provided by China.

The search has thus far focused on a 120,000 sq km (46,330 square miles) band of sea floor in the remote southern Indian Ocean, where the plane is believed to have gone down.

Truss, flanked by officials from the Australian Transport Safety Bureau (ATSB) and Department of Defence, identified an area at the southern tip of that search band that is now believed to be the likeliest resting place of the wreckage.

The area, described by Truss as a "purple patch", had been chosen based on an analysis of the flight data, path and information gleaned from global satellite networks.

"We have a high level of confidence that we are searching in the right area," Assistant Minister for Defence Darren Chester told a media conference in Canberra.

A piece of the plane found washed up on the French island of Reunion in July provided the first direct evidence that the plane had crashed into the sea. No further trace has been found.

Experts involved in past deep-water searches have said the hunt could easily miss the plane because Dutch company Fugro NV was using inappropriate technology and inexperienced personnel for the highly specialized task.

Fugro did not respond to requests for comment when that criticism was made.

US firm Williamson & Associates said images of the southern Indian Ocean floor released by the ATSB in October bore a striking similarity to the underwater debris field Air France Flight 447 left on the Atlantic Ocean floor when it crashed in 2009, killing all 228 passengers and crew.

More than 70,000 sq km have already been checked. The search of the entire band was expected to be completed by June 2016, Truss said. – Reuters