The Dutch Safety Board (DSB) later on Tuesday will release a preliminary report on the downing of Malaysian Airlines Flight MH17 in eastern Ukraine, believed to have been caused by a Russian missile fired in territory held by Moscow-backed rebels.

The DSB aviation investigators are working with information gleaned from the black box flight data recorders, as well as air traffic control, satellite images, and photos from the scene.  It’s far from the final word, and will not assign blame, but it’s an important look at the evidence gathered and analyzed so far.

298 people were killed in the crash in July, including 38 Australian citizens and residents.

Kiev, the US, UK, and European allies say the evidence points to pro-Russian separatists shooting down the plane with a Russian Buk anti-aircraft system.  And now, purported eyewitness have told the BBC that it was Russians, not Ukrainian rebels, at the controls of a Buk.  They were “well-disciplined, unlike the rebels, and not wearing the standard Ukrainian camouflage uniform sported by government and rebel troops alike”, according to the witnesses, and “they had pure Russian accents”.

Russia has consistently denied allegations that it had supplied any missiles or weapons to the rebels.