Investigators have determined that the engines of the Polish state Tupolev Tu-154 which crashed in Russia were operational before it struck the ground.
The inquiry team is synchronising the information from the cockpit-voice and flight-data recorders but hopes to complete this work before the end of this week.
Interstate Aviation Committee head Tatyana Anodina says the Soloviev D-30KU engines were "in working order" until the aircraft collided with an obstacle.
She adds that preliminary analysis of the recorders shows no evidence of in-flight fire or explosion.
The aircraft, arriving from Warsaw with a senior Polish state delegation, had been approaching runway 26 at Smolensk's northern military airfield, in fog, on 10 April.
Images from the scene show that the jet's wreckage is displaced to the left of the runway's extended centreline, and that the direction of the debris trail bears some 30° to the left of the runway heading.
Anodina says the analysis of the flight recorders reveals no evidence of an on-board equipment failure. "Final conclusions will be reachedafter a careful examination of all the fragments," she says.
She adds that another recording instrument has been located, although she has not detailed the find beyond stating that Polish specialists will decode the device.
Investigators are shortly to complete field work on the aircraft's final trajectory. Wreckage of the Tu-154 is to be transferred to a secure area in order to ease the process of analysing the aircraft parts.