The cause of the crash of Azerbaijan Airlines flight J2-8243 near the city of Aktau, Kazakhstan, is still unknown. The Kremlin has so far been tight-lipped, prompting questions over its messaging.

The plane, which crashed in Kazakhstan this week, went down “due to external physical and technical interference,” according to the investigation’s preliminary findings.

Azerbaijan’s flag carrier has announced the suspension of flights to several Russian airports, citing potential flight safety risks following a crash of one of its planes that many experts have blamed on Russian air defense fire.