Investigators have cleared all 227 passengers of any role in hijacking or sabotage and of having personal or psychological issues that might have played a role in the plane's disappearance on March 8, Inspector-General Khalid Abu Bakar said.
There were 14 nationalities represented in the 227 passengers and 12 crew travelling from Kuala Lumpur to Beijing. The majority - 153 people - were Chinese. There were five Indians and one Canadian of Indian-origin.
Investigators believe the Beijing-bound flight was diverted deliberately by someone on board not long after taking off from here. But with no wreckage from the Boeing 777-200 yet detected, despite a massive multi-nation hunt in the southern Indian Ocean, they have few clues to help them determine who caused the diversion and whether it was malicious.
"We have to clear every little thing," Khalid told reporters after a speech at a police academy here. "You cannot hurry us in whatever we are doing."
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Among the things included in "every little thing" is an investigation into the people who prepared the food for the flight. "That also we'll have to look into," he said.
The investigation into what may have caused the plane to appear to vanish on a flight from Kuala Lumpur to Beijing has been a criminal one since March 16, the inspector general said.
He said police were also investigating the cargo and even the food served on the plane to eliminate possible sabotage. Airline rules require pilots and co-pilots to eat different meals in case of food poisoning.
Relatives of the 227 passengers, particularly the many Chinese citizens, have criticised the handling of the search and investigation, and confusing or contradictory statements by Malaysian authorities.