Investigators are trying to restore files deleted last month from the home flight simulator of the pilot aboard the missing Malaysian plane.
Defence minister Hishammuddin Hussein told a news conference that the pilot, Captain Zaharie Ahmad Shah, is considered innocent until proven guilty of any wrongdoing. He said members of Zaharie's family are co-operating in the investigation.
Files containing records of the simulations carried out on the programme were deleted on February 3, Malaysian police chief Khalid Abu told the news conference.
Malaysia Airlines Flight 370 with 239 people aboard went missing March 8 on a night flight from Kuala Lumpur to Beijing. Malaysian authorities have not ruled out any possible explanations, but have said the evidence so far suggests the flight was deliberately turned back across Malaysia to the Strait of Malacca. They are unsure what happened next.
Investigators have identified two giant arcs of territory spanning the possible positions of the plane about seven-and-a-half hours after take-off, based on its last signal to a satellite. The arcs stretch up as far as Kazakhstan in central Asia and down deep into the southern Indian Ocean.
Police are considering the possibility of hijacking, sabotage, terrorism or issues related to the mental health of the pilots or anyone else on board, and have asked for background checks from foreign agencies on all foreign passengers.
Mr Hishammuddin said background checks have been received for all the foreigners except those from Ukraine and Russia - which account for three passengers. He said none of the checks has turned up anything suspicious.