International investigators say the missile that downed Malaysian Airlines flight MH17 was from a 'Russian brigade'.
All 298 people on board were killed when the plane headed from Amsterdam to Kuala Lumpur crashed in July 2014.
Experts have been analysing video images as they work to figure out what happened.
They had previously said that the plane was shot down from the ground, by a BUK missile moved into Ukraine from Russia.
Providing an update today, the investigators said: "The [Joint Investigation Team] is convinced that the BUK TELAR that was used to down MH17, originates from the 53rd Anti Aircraft Missile brigade... a unit of the Russian army from Kursk in the Russian Federation.
"The JIT reached this conclusion after extensive comparative research."
Russia has always denied any responsibility.
Any prosecutions will take place in the Netherlands, and investigators have said they are focusing on around 100 people they believe could be 'associated' with the downing of the plane.
Today, a prosecutor said any allegations about individuals' involvement will be detailed in any court case, noting: "It can damage the investigation and the ultimate legal procedure if we make it clear to those responsible for this event – and those further involved – how much we know exactly."