"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 here.
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, Bakar 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. 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 onboard the airliner that went mysteriously missing on March 8 after its take-off from Kuala Lumpur with 239 people onboard.
Khalid Abu Bakar said the police had to scrutinise carefully to rule out sabotage. "For example, when we knew there was a load of mangosteens onboard, we had to find out where the mangosteens came from.
We tracked down who plucked the fruits, who packed them and shipped them out, and who put them on the plane. "Then we had to determine who would have received them in China and who paid for it, and for how much. Imagine how many people we must interview to rule out sabotage and that is just the mangosteens," Khalid said.
Over 170 statements from foreign and local sources as well as the families of passengers and crew aboard MH370 have been recorded. "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. Khalid warned that authorities may never know what caused the disappearance of flight MH370. 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 were still awaiting feedback.