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.

We will never forget the beloved people we lost in the crash of the Embraer 190 aircraft,” said Azerbaijan Airlines in a statement posted online on Boxing Day. The pro-government AnewZ news station cited Azerbaijan officials as saying shrapnel from a Russian missile was responsible.

The Azerbaijan Airlines Embraer 190 flight left Baku, Azerbaijan, on Christmas to Grozny, Russia. Instead, the plane crashed in Aktau, Kazakhstan.