The real cause behind the mysterious disappearance of Flight MH370 may never be known, Malaysian police warned today as the frustrating search for the crashed airliner continued in the Indian Ocean without any headway.
"Criminal investigations may go on and on and on. We have to clear every little thing," Inspector-General of Police Khalid Abu Bakar said.
"At the end of the investigations, we may not even know the real cause. We may not even know the reason for this incident," he told reporters in Kuala Lumpur.
After intense investigations, some clues into the missing MH370 have been derived after interrogating 170 people, including family members of passengers, pilot and co-pilot, Khalid said, adding that more people will be quizzed.
It was not known how strong the leads were as the official did not elaborate. "I do not wish to comment on the background checking of the pilot or cabin crew as they are the subjects of investigations. All passengers have been cleared of the four focus areas of probe - personal and psychological problems, sabotage and hijacking," he said.
The Boeing 777-200's cargo of mangosteens has also come under scrutiny besides the food served on board the Beijing-bound airliner that disappeared from radar screens on March 8, one hour after taking off. Khalid said the police had to scrutinise carefully to rule out sabotage.
"We must be very thorough and we need all the time ... you cannot hurry us," he said. The police is treating the case as a criminal probe. Malaysian Prime Minister Najib Razak will be in Perth on a two-day tour to oversee the search for the plane.
Malaysia has came under criticism from aviation experts and families of the 239 victims of the plane crash over handling the probe. On the 25th day of the multinational search operations, a British nuclear submarine joined the hunt for the plane in the Indian Ocean.
According to media reports here, Britain's Royal Navy submarine HMS Tireless arrived in the search area about 1,500 kilometres northwest of Perth this morning. The personal jet of Peter Jackson - Oscar-winning New Zealand movie director - is also being used in the hunt.
Up to 10 planes and nine ships participated in today's search for the Boeing 777-200, the Joint Agency Co-ordination Centre (JACC) in Perth managing the operations said in a statement.
The Australian Maritime Safety Authority has determined a search area of about 221,000 square kilometres, 1,504 kilometres northwest of Perth.
Retired Australian Air Chief Marshal Angus Houston, heading the JACC, yesterday said it was the most challenging search and rescue operation he had ever seen and said efforts to trace the wreckage could take time.
He said the task was "very complex", "very demanding" because the teams had no hard information to work from. Houston said no time frame had been set for the search to end, but that a new approach would be needed if nothing showed up.
"Over time, if we don't find anything on the surface, we're going to have to think about what we do next, because clearly it's vitally important for the families, it's vitally important for the governments involved that we find this airplane," he told ABC news.
Yesterday, Malaysian authorities released the full transcript of the communications between flight MH370 and air traffic control, revising its earlier account of the final words from the cockpit.
The transcript shows the last voice transmission from the doomed Boeing 777-200 plane was "Good night Malaysian three- seven-zero," not the "All right, good night" transmission authorities had previously used.
It is not clear why the official account has changed now. Many frustrated family members of those on board have been accusing officials of mishandling the search, and the latest change may add to their mistrust of the Malaysian authorities.
The flight's captain, Zaharie Ahmad Shah, 53, and First Officer Fariq Abdul Hamid, 27, have come under close scrutiny as investigators believe the plane was deliberately diverted by someone on board.
Zaharie's flight simulator is being examined and Malaysian authorities today organised a closed-door briefing in Malaysia for the families with officials and experts involved in the hunt and showed them the satellite data which led them to conclude that the flight ended in the southern Indian Ocean.
But the families said they were not satisfied with the explanation.