Azerbaijan held a day of mourning on Thursday for the dozens of victims of an airliner crash in Kazakhstan, as questions were being asked over the cause of the disaster.

The preliminary results of Azerbaijan’s investigation into the deadly crash of a civilian airliner point to the plane being hit by a Russian antiaircraft missile, or shrapnel from it, said people briefed on the probe.

The flight was en route from the Azerbaijani capital of Baku to Grozny, in Russia’s south, when it diverted and attempted an emergency landing in Kazakhstan.