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.

Azerbaijan enacted a national day of mourning on Thursday following a plane crash that killed 38 passengers and left 29 survivors. The Azerbaijan Airlines Embraer 190 flight left Baku, Azerbaijan, on Wednesday and was slated to land in Grozny,

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.