The crash of an Azerbaijani airliner in Kazakhstan has killed 38 of 67 people on board. Azerbaijan Airlines’ Embraer 190 was en route from Azerbaijani capital Baku to the Russian city of Grozny in the North Caucasus on Wednesday when it was diverted for reasons that aren’t fully clear yet.

T hursday is an official day of mourning in Azerbaijan as an investigation is underway to determine what caused an airplane carrying 67 passengers to crash on Christmas Day in Kazakhstan, killing 38 and leaving at least 29 survivors. Video posted by CNN shows the plane crash-landing, exploding into a fireball and plumes of black smoke.

Russian President Vladimir Putin apologized for the deadly Azerbaijan Airlines Flight 8243 crash on Christmas but did not take responsibility for causing it as an investigation continues into the matter.