Questions were being asked Thursday about the cause of an airliner crash in Kazakhstan the day before, as Azerbaijan held a day of mourning for the dozens of victims of the disaster. The reasons that Azerbaijan Airlines flight J2-8243 came down are still unknown.

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.