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.

Azerbaijan Airlines flight J2-8243 caught fire as it tried to make an emergency landing in Aktau, southwestern Kazakhstan, on Wednesday. It was traveling from the Azeri capital Baku to Grozny, the capital of the Russian republic of Chechnya.

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.

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.

On Christmas Day, a plane traveling from Baku, Azerbaijan, to Grozny, Russia, crashed in Kazakhstan, killing over half of its passengers. Theories abound regarding why the plane made an emergency landing near the Kazakhstani city of Aktau.

An Azerbaijan Airlines statement on Dec. 27 blamed “interference” for the Christmas Day plane crash that killed 38 people.

Russian President Vladimir Putin apologized to his Azerbaijani counterpart after an incident in Russian airspace that led to the crash of an Azerbaijan Airlines passenger aircraft on Dec. 25, killing dozens.