Mobile phone footage circulating online appeared to show the Azerbaijani Airlines plane making a steep descent before slamming into the ground in a fireball in western Kazakhstan.

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.

The voice recorders from the Brazilian-made plane were analyzed in Brasilia before the data was handed to Kazakh authorities. Meanwhile, Azerbaijan has directed unusually strong words towards Moscow.

Azerbaijan Airlines’ Embraer 190 was en route from the Azerbaijani capital of Baku to Grozny in the North Caucasus on Wednesday when it was diverted. It crashed while trying to land near the city of Aktau, Kazakhstan, after flying hundreds of kilometers (miles) east across the Caspian Sea.

The extraction of flight data from the Brazilian-made Azerbaijan Airlines plane that crashed in Kazakhstan last month was completed at a lab run by Brazil's air force, according to a statement released by the entity on Monday.

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.

Flight records for the plane made by Brazil's Embraer that crashed last week in Kazakhstan are headed to the South American country so the data can be extracted, the Brazilian Air Force said in a statement on Monday.

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.

The Brazilian Air Force Laboratory has sent data from the flight recorders of an Azerbaijan Airlines plane to Kazakh investigators. The plane crashed on December 25 near the city of Aktau, Radio Liberty reports.