The extraction of flight data from the Brazilian-made Azerbaijan Airlines 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.

After an Azerbaijan Airlines plane crashed in Kazakhstan in December, killing 38 people, a video surfaced across social media in multiple languages alongside the claim it showed the moments before the tragedy.

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.

On 25 December, 38 people died when an Azerbaijan Airlines flight, which had been due to land in Russia, crash-landed in Kazakhstan. The circumstances around the crash remain unclear, but limited evidence so far suggests it may have been damaged by missiles fired by a Russian air-defence system as it tried to land in Chechnya.

The cause of the crash of Azerbaijan Airlines flight J2-8243 near the city of Aktau, Kazakhstan, is still unknown. The Kremlin has so far been tight-lipped, prompting questions over its messaging.

Azerbaijan Airlines Flight 8243 was scheduled to travel from Baku, the capital of Azerbaijan, to Grozny, a city in the Russian region of Chechnya, on Wednesday, but was diverted and ultimately crashed on the other side of the Caspian Sea, less than two miles from the airport in Aktau, Kazakhstan.

The flight was en route from the Azerbaijani capital of Baku to Grozny, in Russia’s south, when it diverted and attempted an emergency landing in Kazakhstan.

In the crash’s aftermath, Azerbaijan has unleashed rare and stinging criticism of Russia, with the country’s president saying Moscow’s response has caused “surprise, regret and rightful indignation.”