Malaysia is worried the black box recording devices of MH17 will be tampered with to protect those who shot down the plane, as a United Nations' agency said Ukraine would be officially in-charge of investigations into the crash.
Malaysia's prime minister Najib Razak said after meeting relatives of victims that the black boxes are owned by Malaysia.
"Those who have no rights whatsoever cannot claim or take control of the black box," he said.
Aviation experts say the boxes, which contain cockpit and data recordings, would establish for certain where the surface-to-air missile that brought the Boeing 777 down was fired from.
Malaysia's minister of transport Liow Tiong Lai said his country does not know whether the devices have been recovered from the crash site in eastern Ukraine.
Within hours of the crash there were unconfirmed reports the black boxes had been sent to Moscow.
Australian aviation expert Desmond Ross said it is crucial the black boxes be kept safe and taken to an independent authorised laboratory.
"That will tell us almost everything," Captain Ross said.
"I am concerned that if, as is being reported, the Russians have them, they may be altered or that some data will mysteriously disappear," he said.
The International Civil Aviation Organisation (ICAO), the Montreal-based UN agency regulating aviation, said under international conventions Ukraine will be officially in-charge of the investigation because the plane crashed there.
But the ICAO said in a statement that other countries will also be to participate or appoint experts to the investigation, which will presumably include Malaysia and other countries whose citizens were killed, including Australia.
- Sydney Morning Herald