Fragments of a suspected Russian missile system have been found at the Flight MH17 crash site in Ukraine, investigators in the Netherlands say.
The parts, possibly from a Buk surface-to-air system, are "of particular interest" and could help show who was behind the crash, they said.
But they said they had not yet proved their "causal connection" with the crash.
MH17 crashed on land held by Russian-backed rebels in July 2014, killing all 298 on board.
There were 283 passengers, including 80 children, and 15 crew members on the Malaysian Airlines airliner.
About two-thirds of those who died were Dutch nationals, with dozens of Malaysians and Australians among the rest.
Ukraine and many Western countries have accused pro-Russian rebels of shooting down the plane, saying they could have used a Buk missile system supplied by Russia.
Russia and the rebels deny any responsibility and say the Ukrainian military was to blame.
The Joint Investigation Team (JIT) said in a statement with the Dutch Safety Board that the parts had been "secured during a previous recovery mission in eastern Ukraine".
"The parts are of particular interest to the criminal investigation as they can possibly provide more information about who was involved in the crash of MH17. For that reason the JIT further investigates the origin of these parts," the statement said.
Fred Westerbeke, a spokesman for the Dutch Prosecutor's Office, said that seven fragments had been found which were definitely not part of the aircraft, and further investigations had shown that they were probably from a missile system.
"We are going to need more investigation to really find out what exactly this is and if it is part of a possible system that took down MH17," he added.
"If we can establish that, then we can say that it is a breakthrough."