Malaysia's police chief, Inspector General Khalid Abu Bakar, addresses a news conference on the two passengers who had travelled onboard the missing Malaysia Airlines MH370 plane on stolen passports in Kuala Lumpur International Airport March 11, 2014. [Photo / Agencies]

KUALA LUMPUR - Malaysia police chief said Wednesday Flight MH370 probe was classified as a criminal investigation.

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The search for missing Malaysia Airlines flight MH370 was a criminal investigation, and there were things Malaysia police authorities could not share, local newspaper New Straits Times reported, quoting Malaysian Inspector General of Police Khalid Abu Bakar.

"We are investigating the four areas of focus, namely, personal and psychological problems, sabotage and hijacking," Khalid said at a press conference after opening the Royal Malaysian Police Quality and Innovation Seminar 2014.

He said until now there had been about 170 statements recorded from family members of the passengers and crew on board the missing jetliner.

Khalid said the investigators did have some clues of what happened, but they would not reveal anything as the investigation was ongoing.

Khalid's remarks came two days after the last words from the cockpit of MH370 were updated.

Earlier reports said the last words from the cockpit were "All right, goodnight", and the Malaysia Airlines said later on that the initial investigation indicated that the voice was from the co-pilot Fariq Abdul Hamid.

The latest updates of the "last words" issue revealed the last conversation between the air traffic controller and the cockpit was at 1:19 am and the account of the last words were changed as "Good night Malaysian three seven zero." Malaysian authorities said they were still conducting "forensic investigation" to determine whether the last words from the cockpit were by the pilot or the co-pilot.

Full transcript of MH370 pilot communications revealed