PERTH, Australia (AFP) - Two vessels searched underwater for missing Malaysia Airlines Flight MH370 on Saturday, as air and sea missions failed to find any sign of the plane and the clock ticked on the signal from its black box.
Up to 10 military planes, three civilian jets and 11 ships took part in the protracted search in the southern Indian Ocean for the Boeing 777 which disappeared on March 8 with 239 people onboard.
"Today Australian Defence Vessel Ocean Shield and (Britain's) HMS Echo continue underwater search operations," the Joint Agency Coordination Centre (JACC) said.
The vessels, which are searching 24 hours a day, hope to pick up a signal from the plane's black box recorder, but the battery powering those emissions is nearing the end of its roughly 30-day life span.
In Kuala Lumpur, Transport Minister Hishammuddin Hussein said Malaysia would, in line with international agreements, appoint an independent "investigator in charge" to lead an international team to probe what happened to MH370.
The team will include Australia, China, the United States, Britain and France.
Mr Hishammuddin again declined to provide any detail from Malaysia's ongoing investigation, however, saying he remained focused on finding the plane and its black box.
"In spite of (the long odds), our determination remains undiminished," he told a press briefing.
Australia is leading the hunt for the plane, which concentrated Saturday on about 217,000 square kilometres of the Indian Ocean some 1,700 kilometres north-west of Perth.
Malaysian authorities believe satellite readings indicates MH370 crashed in the Indian Ocean, far off Australia's western coastline, after veering dramatically off course during a flight from Kuala Lumpur to Beijing.
But no proof has been found that would indicate a crash site, and Australian Prime Minister Tony Abbott has described the oceanic search as "the most difficult in human history".
- Slow progress -
The JACC said Australia's Transport Safety Bureau was continuing "to refine the area where the aircraft entered the water" using further analysis of satellite data and aircraft performance.
Several nations that normally do not work together - notably the United States and China - have rallied to help look for clues in one of the world's greatest-ever aviation mysteries.
Authorities still have no idea how or why the plane vanished, and warn that unless the black box is found, the mystery may never be solved.
The Ocean Shield, which is carrying a US Navy "black box" detector, and HMS Echo, which has a similar capability, are searching a 240-kilometre track of ocean in hopes of detecting sonic pings from the recorder.
However, progress is painstaking as vessels must move slowly to improve readings, and officials have acknowledge there is no solid evidence the plane went down in that stretch of sea.
"The search using sub-surface equipment needs to be methodical and carefully executed in order to effectively detect the faint signal of the pinger," Commodore Peter Leavy said.
- Malaysia rejects accusations -
Malaysia has come under harsh criticism from Chinese families - most of the 227 passengers were from China - for the unprecedented loss of a jumbo jet, and pressure from China's government over a seemingly confused response marked by contradictory statements.
The mixed messages continued on Saturday, with Mr Hishammuddin denying that investigations had cleared anyone aboard MH370 of suspicion, despite Malaysia's police chief saying last week that all passengers had indeed been cleared.
"I dont think anybody has been cleared from any of the investigations," Hishammuddin said.
He also dismissed as "completely untrue" any suggestions that Malaysian authorities were to blame for the loss of the plane.
He was apparently referring to opposition leader Anwar Ibrahim who, in a newspaper interview Thursday, accused the Malaysia's long-ruling authoritarian regime - which has a track record of sweeping scandals under the rug - of withholding information.
Anwar also criticised the government for failing to respond when the plane was detected on military radar heading off-course toward the Indian Ocean on March 8.
"Whether they ignored it, or failed to detect it because of incompetence is the question which has not been answered and is still being dodged by the authorities," Anwar told AFP on Saturday.
"That opens up all manner of speculation including a possible cover-up."