The location of Flight MH370 has become one of the world’s greatest aviation mysteries since the plane, a Boeing 777, disappeared in 2014 en route to Beijing from the Malaysian capital of Kuala Lumpur with 239 people on board.

“I don’t rule out a future underwater search by any stretch,” Australian Transport Minister Darren Chester told reporters in Melbourne, a day after Australia, Malaysia and China officially called off the search in the southern Indian Ocean.

The search cost around A$200 million ($150 million), mostly paid by Malaysia, and has already been extended twice. But the three countries involved have been reluctant to keep looking without new evidence about the plane’s final resting place.

A recommendation from investigators last month to look to the north of the 120,000 sq k.m. (46,000 sq mile) area that has been the focus of search efforts was rejected by Australia and Malaysia as too imprecise.

Chester said cost had not been the determining factor to halt the search, but he said restarting it would require “credible new information which leads to a specific location”.

Australian Prime Minister Malcolm Turnbull on Wednesday expressed “deep regret” that the plane had not been found, but reaffirmed the agreement between Malaysia, Australia and China to stop looking.

Boeing did not immediately respond to requests for comment.

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No Clues

Flight MH370 lost contact over the Gulf of Thailand in the early hours of March 8, 2014. Subsequent analysis of radar and satellite contacts suggested someone on board may have deliberately switched off the plane’s transponder before diverting it thousands of kilometers out over the Indian Ocean.

Since the crash, there have been competing theories over whether the plane was hijacked and whether it was under the control of anyone when it finally ran out of fuel.

The head of the Australian Transport Safety Bureau (ATSB), which led the hunt for the plane, said authorities are confident it is not in the area that has been searched.

ATSB chief commissioner Greg Hood said “residual search activity,” including satellite and drift analysis would continue until the end of February.

But quitting the underwater search drew a swift and angry reaction from relatives of those on board, who had called for the project to be expanded.

In China, Jiang Hui, whose mother was also on board the flight, said he felt “disappointed, helpless and angry” because the search had been ended.

There was also anger on social media at the news.

“Didn’t they say they would never end the search? What the hell happened?” wrote one user on China’s Twitter-like Weibo service.

The only confirmed traces of the plane have been three pieces of debris found washed up on the island country Mauritius, the French island Reunion and an island off Tanzania.

As many as 30 other pieces of wreckage found there and on beaches in Mozambique, Tanzania and South Africa are suspected to have come from the plane.