Experts say evidence in the Azerbaijan Airlines plane crash in Kazakhstan points to a possible midair explosion, not an encounter with a flock of birds.

The Embraer 190 was traveling to Grozny, Russia, but crashed near Aktau, Kazakhstan, killing 38 people onboard. Investigators are focusing on Russian air defense as the likely cause.

U.S. officials say Russia could be behind a passenger plane crash in Kazakhstan that left at least 38 dead Wednesday, but Russia is denying any involvement.