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.

Of 62 passengers and five crew members on board the Azerbaijan Airlines flight, 29 survived, according to Kazakhstan’s authorities.

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.