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.

Azerbaijan on Thursday observed a nationwide day of mourning for the victims of the plane crash that killed 38 people and left all 29 survivors injured as speculation mounted about a possible cause of the disaster,

Officials in Russia and Kazakhstan are urging people to wait for an investigation into the deadly Azerbaijan Airlines plane crash before assigning blame.