The hunt for missing Malaysia Airlines Flight MH370 will not be expanded beyond its current area without specific new leads, Australian officials said Wednesday, dousing relatives' hopes the search could last beyond early next year.

In April, more than a year after the plane vanished en route from Kuala Lumpur to Beijing with 239 people on board, Malaysia, Australia and China announced that the search zone would double in size.

This boosted the area of the remote southern Indian Ocean being scoured by three specialist vessels to 120,000 square kilometres (46,300 square miles), with officials saying the wider search could take another year due to the difficult conditions.

But on Wednesday, the Australian-led Joint Agency Coordination Centre (JACC) said it would not expand the search -- which has already proved arduous and expensive -- without new data.

"In the absence of credible new information that leads to the identification of a specific location of the aircraft, governments have agreed that there will be no further expansion of the search area," JACC said.

The hunt for the aircraft, which disappeared on March 8 last year, has been a complex undertaking, with Australia initially concentrating on a remote 60,000 square kilometre area of the ocean far off its west coast.

No wreckage from MH370 has ever been found in one of aviation's great mysteries and Malaysian authorities in January declared that all on board were presumed dead.

But many relatives of those lost on the flight have rejected that verdict, criticising Malaysia's handling of the situation and questioning the choice to focus the search on the southern Indian Ocean.

- Families not satisfied -

"We do not know for sure where the plane is even after such a long time. Hence we demand they expand the area of search until the plane is found," 61-year-old Malaysian G. Subramaniam, whose only son was on the flight, told AFP on Wednesday.

"Every day is a difficult day for me and my wife. Until a wreckage is found, we will not accept the claim by the authorities that the plane has crashed."

The search zone -- a sweeping arc about 1,600 kilometres -- was determined by analysing data from satellite signals which indicate the plane went down in the Indian Ocean after mysteriously diverting.

More than 50,000 square kilometres of the seafloor have been scoured so far with no trace of the jet, JACC said, and with the onset of winter and poor weather the operation is slowing down.

The deep underwater search using sonar equipment is currently suspended due to choppy seas, where waves have reached up to 12 metres (39 feet), although ships remain on the scene.

It will continue once conditions improve but be scaled back with one of the vessels, GO Phoenix, ceasing operations and returning to Singapore near the end of June.

A fourth vessel previously involved in the search, Fugro Supporter, which carried an autonomous underwater vehicle, was withdrawn in May in the face of the worsening conditions.

"Safety of the search crews, as always, remains a priority and vessels and equipment utilised will vary to reflect operational needs, particularly during winter months," JACC said.

"Search operations will continue through the winter months, but pauses are anticipated."

The pitch-black extreme depths of up to 4,000 metres (13,000 feet) in the search area as well as the rugged nature of the seafloor have also added to the challenges facing authorities.

The hunt has also far uncovered a previously uncharted shipwreck deep underwater, authorities said last month.

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Malaysia Airlines