Data was deleted from the home flight simulator used by one of the pilots of missing Malaysia Airlines flight 370, according to Malaysian officials.
Khalid Abu Bakar, Malaysia's police chief, said the data log of Zaharie Ahmad Shah's simulator's had been cleared on February 3.
Police have searched the homes of the Zaharie, 53, and co-pilot Fariq Abdul Hamid, 27. Among the items taken were a the flight simulator that Zaharie had built in his home.
Hishammuddin Hussein, the country's minister of transport and defence, said on Wednesday that investigators were trying to recover the information.
He added that background checks on all but three of the 239 passengers on board the aircraft when it disappeared on March 8 had produced no "information of significance," the AFP news agency reported.
The methodical shutdown of the communications systems, together with the fact that the plane appeared to be following a planned course after turning back, have been interpreted as suggesting strongly that foul play, rather than some kind of technical failure, was behind the disappearance.
US government sources said intelligence agencies had extensively analysed people on the flight but came up with no connections to possible sinister motives. A senior US official said he was "not aware of any stones left unturned".
Teams from 26 countries are helping with the search effort, with Australia taking the lead in the southern part of the Indian ocean, with assistance from the US navy.
It has shrunk its search field based on satellite tracking data and analysis of weather and currents, but it still covers an area of 600,000 sq km, roughly the size of Spain and Portugal.