Rebels in eastern Ukraine have handed over two flight-data recorders from the downed MH17 plane to Malaysian experts.
A senior rebel leader signed them over to the Malaysian officials at a meeting in the city of Donetsk.
The handover came hours after the UN Security Council voted unanimously to demand immediate international access to the crash site.
The Malaysian Airlines passenger jet crashed last Thursday, killing all 298 people on board.
Western nations say there is growing evidence that flight MH17 was hit by a Russian-supplied missile fired by rebels.
‘In good condition’
Experts say the “black boxes” will reveal the exact time of the incident and the altitude and exact position of the aircraft.
They should also contain the cockpit voice recorder, which it is hoped will provide clues as to what the cause of the crash was.
The head of the Malaysian delegation told reporters that the recorders were “in good condition”.
The Malaysian experts and a Dutch delegation will travel with the train to the city of Kharkiv on Tuesday.
Meanwhile a UN resolution, proposed by Australia, was passed calling for a “full, thorough and independent international investigation” into the downing of the plane over Grabove on 17 July.
It also demanded that those responsible “be held to account and that all states co-operate fully with efforts to establish accountability”.
There has been international outcry over the way rebels have handled the situation, leaving passengers’ remains exposed to summer heat and allowing untrained volunteers to comb through the area.
All 15 council members, including Russia, voted in favour.
On Monday, three Dutch experts became the first international investigators to examine the bodies of the victims. They said the storage of the bodies had been “of good quality”.
The train’s departure came after tough negotiations between the international community and the separatists, who had been accused of limiting access to the crash site.
US President Barack Obama called on Russian President Vladimir Putin to stop the rebels from hampering the investigation at the crash site.
“What exactly are they trying to hide?” Mr Obama said on Monday.
He also warned Mr Putin that he could face additional economic costs if he fails to take steps to resolve the crisis in Ukraine.
British Prime Minister David Cameron said there was strong evidence that pro-Russian separatists shot down the plane with an anti-aircraft system known as Buk.
Russia on Monday again denied allegations that it had supplied such missiles or “any other weapons” to the rebels.
The defence ministry said a Ukrainian military plane had flown within firing range of the airliner just before it came down, but Ukrainian President Petro Poroshenko has rejected the claim.
The fighting in eastern Ukraine erupted in April and is believed to have claimed more than 1,000 lives.
Battles continued on Monday, with heavy clashes around the main rebel-held city of Donetsk.
At least three civilians were reported killed, and one multi-storey building was seen on fire.