This article is more than 6 years old

This article is more than 6 years old

Deep-sea microphones picked up an intense sound that may have been Malaysian Airlines flight MH370 crashing into the Indian Ocean, Australian researchers have announced – while stressing that the likelihood of a connection to the plane could be as low as 10% and a natural event like an earthquake might also have been the source.

Scientists from Curtin University in Western Australia gave a highly cautious account on Wednesday after analysing low-frequency noises picked up by a combination of underwater sensors – some set up by the UN to monitor for nuclear tests, and others put in place for Australian research purposes.

The Malaysian Airliner went missing almost three months ago on a flight from Kuala Lumpur to Beijing with 239 people on board. Satellite signals point to the plane having gone down in the Indian Ocean but a massive international search effort led by Australia has turned up nothing.

Underwater sound recorders from Curtin University’s Centre of Marine Science, placed about 40km off Rottnest Island, picked up a signal on 8 March that may have represented a "high-energy event" around the time the plane was thought to have crashed, said Dr Alec Duncan, a senior research fellow at the centre.

The signal was matched with another underwater listening station, run by the United Nations' Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO), off Cape Leeuwin, the most south-westerly mainland point of the Australia.

“Soon after the aircraft disappeared scientists at CTBTO analysed data from their underwater listening stations south-west of Cape Leeuwin and in the northern Indian Ocean,” he said. That initially did not turn up anything of interest, Duncan said.

When the search for MH70 swung to the southern Indian Ocean scientists from Curtin decided to retrieve their acoustic recorders from west of Rottnest Island, to be checked against the CTBTO's earlier data, Duncan said.

“Data from one of the IMOS recorders showed a clear acoustic signal at a time that was reasonably consistent with the information relating to the disappearance of MH370," he said.

The CTBO analysis was rechecked and revealed a signal "almost buried in the background noise but consistent with what was recorded on the IMOS recorder off Rottnest”, Duncan said.

“The crash of a large aircraft in the ocean would be a high-energy event and expected to generate intense underwater sounds. The timing of the signal was not totally unrelated to the disappearance of the plane.”

Duncan said he had sent the results to the Australian Transport Safety Bureau and scientists at Curtin would continue to work with authorities, he said.

Duncan cautioned that large uncertainties in the estimates meant it was only a possibility that the sound came from MH370, and a natural event like an earth tremor could be equally or more likely.

“Although we have now completed our analysis of these signals, [we] still have several recorders deployed that could conceivably have picked up signals relating to MH370,” he said.

“If it is related to the aircraft it could reduce the size of the search area.”

Despite millions of dollars spent on the search, with sophisticated underwater equipment including drone submersibles used to sweep a vast area of the Indian Ocean, nothing has been found.

In recent days Australian authorities announced that the much-heralded detection of underwater "pings" thought to have come from the plane's black box flight recorders was probably a false lead.