The missile that downed a Malaysia Airlines flight over eastern Ukraine in 2014 belonged to a Russian brigade, international investigators say.
For the first time, the Dutch-led team said the missile had come from a unit based in western Russia.
All 298 people on board the Boeing 777 died when it broke apart in mid-air flying from Amsterdam to Kuala Lumpur.
It was hit by a missile fired from rebel-held territory in Ukraine. Russia says none of its weapons was used.
But on Thursday Wilbert Paulissen, a Dutch official from the Joint Investigation Team (JIT), told reporters: "All the vehicles in a convoy carrying the missile were part of the Russian armed forces."
He said that after studying all available photos and footage, investigators had been able to trace the convoy to Russia's 53rd brigade, which consists of 300 people based in the city of Kursk.
What happened to MH17?
The incident occurred at the height of the conflict between government troops and pro-Russian separatists.
The plane left Amsterdam's Schiphol Airport on 17 July 2014 and was due to arrive at Kuala Lumpur in Malaysia on the following day.
The plane lost contact with air traffic control about 50km (30 miles) from the Russia-Ukraine border.
It crashed in the Donetsk area, in territory controlled by pro-Russian separatists.
Footage was later released by the Ukrainian government suggesting that a Russian-made Buk missile had been moved across the Russian border the next day.
What has been said about the incident?
In October 2015 the Dutch Safety Board concluded that the plane had indeed been hit by a Buk missile.
September 2016, the JIT - which includes officials from the Netherlands, Australia, Belgium, Malaysia and Ukraine - reached a similar conclusion in a preliminary report.
It said it had "irrefutable evidence" that the missile had been brought in from Russian territory and fired from a field controlled by pro-Russian fighters.
The investigators simulated various trajectories of the warhead. They showed it had exploded metres above the aeroplane's nose, showering the aircraft with fragments.
Russia has repeatedly denied that its forces were involved.
