Investigators attempting to explain the crash of the Polish presidential Tupolev Tu-154 at Smolensk are interviewing the crew of a Yakovlev Yak-40 from the same presidential squadron which successfully landed ahead of the ill-fated jet.
Russia's Interstate Aviation Committee adds that a working group is still filtering the Tu-154's cockpit-voice recorder to eliminate extraneous noise and identify parts of the conversation record.
The Polish prosecutor general's office states that the Yak-40 crew transmitted a warning by radio to the Tu-154 pilots regarding the worsening weather conditions at Smolensk.
Another aircraft, an Ilyushin Il-76, had also conducted test approaches at Smolensk "a few tens of minutes" beforehand, the office adds, before departing.
While the precise time difference has yet to be determined, the office says it was long enough to "exclude the hypothesis" that the Tu-154 was affected by wake turbulence.
The prosecutor's office says the inquiry is studying personal data devices - such as mobile phones, cameras and laptop computers - retrieved from the wreckage to see whether they contain valuable information pertaining to the 10 April accident, and to check whether there was any risk of electronic interference with the Tu-154's systems.
Although the aircraft was delayed in its departure from Warsaw, evidence indicates the Tu-154 was prepared properly and was in "good working order", and that the aircraft's fuel was in line with standards. The prosecutor's office also says there is "no reason to question" the modification work performed by the Samara-based Aviakor plant before the aircraft was returned to Poland last December.
Both pilots knew the Russian language "sufficiently", it says, adding that the crew had undergone strict training. But the office says that it would be "premature", based on evidence so far received, to reject - or accept - the conclusion that the crew's actions contributed directly to the accident.