Pro-Russian rebels operating in the east of Ukraine have handed over two flight-data recorders from the downed MH17 plane to Malaysian experts.
The Malaysian Airlines Boeing 777 crashed last Thursday, killing all 298 people on board.
The ‘black box’ flight recorders will help analysts understand what happened to the aircraft.
Western nations say there is growing evidence that flight MH17 was hit by a Russian-supplied missile fired by rebels.
However, Russia has suggested Ukrainian government forces are to blame.
Data includes the exact time of the incident and the altitude and precise position of the aircraft.
The handover followed talks between the rebel commander Alexander Borodai and Malaysian prime minister Najib Razak.
Discussing the handover my Najib said: “Only then can the investigation into MH17 truly begin; only then can the victims be afforded the respect they deserve.
“We need to know what caused the plane to crash, and who was responsible for it, so that justice may be done.
“In recent days, there were times I wanted to give greater voice to the anger and grief that the Malaysian people feel.
“And that I feel.
“But sometimes, we must work quietly in the service of a better outcome.”
At the same time a train with the remains of victims of crash in Ukraine has arrived in the city of Kharkhiv, outside rebel territory.
Many of the victims were Dutch, with the bodies to be prepared for transfer by air to the Netherlands where forensic experts will evaluate and identify them.