The police have "cleared' all passengers of a missing Malaysian airliner of hijacking, sabotage and psychological and personal problems, but are still investigating the cabin crew including the pilot and co-pilot, said Inspector-General of Police Tan Sri Khalid Abu Bakar.

He said investigation of the 227 passengers of the Malaysia Airlines (MAS) Flight MH370 revealed that they were "free" from the four elements.

"They have been cleared of the four (elements). It (is) according to our own procedure (investigation)," he told reporters after opening a quality-enhancing seminar for the police, Wednesday.

He said the police were still investigating these four areas with regard to the cabin crew, including the pilot and the co-pilot.

Flight MH370, carrying 227 passengers and 12 crew, left the KL International Airport at 12.41 am on March 8 and disappeared from radar screens about an hour later while over the South China Sea. It was to have landed in Beijing at 6.30 am on the same day.

Prime Minister Datuk Seri Najib Tun Razak announced on March 24, seventeen days after the disappearance of the Boeing 777-200 aircraft, that Flight MH370 "ended in the southern Indian Ocean".

Khalid said the police would not release any findings of the investigation into the incident as it would jeopardise the ongoing probe.

"I'm sorry, there are things we cannot reveal to you; not that I don't want to reveal to you but we cannot do that. Because it's a criminal investigation, ongoing; we have not concluded the whole thing and we are still awaiting reports from experts overseas and internally.

"You must understand that. I think we have been very consistent (about the investigation). Who knows, maybe there will be prosecution later on. So, this will affect the prosecution's case if we start revealing our findings," he said.

Khalid said that so far the police had recorded statements from more than 170 individuals over the disappearance of the Boeing 777-200 aircraft, and added that they would record many more statements.