Several of Brazilian air force investigators are working with colleagues from three other nations to analyze data from the Azerbaijani airliner that crashed in Kazakhstan on Dec. 25, killing 38 people. Azerbaijan claims the jet was unintentionally shot down by Russia.

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

Brazil's air force said in a statement late Thursday that nine foreign investigators have gathered with its own experts at its center for investigation and prevention of air accidents in capital Brasilia to work on data extracted from the airplane's black box and other tools. Kazakhstan has three investigators in that group, while six others come from Azerbaijan and Russia.

Investigators in Brasilia are working on recordings, cockpit voice and flight data recorders of the aircraft, the Brazilian air force added. There's no deadline for investigators to publicize their conclusions, which will ultimately come from Kazakh authorities.

“The extraction, obtention and validation of the data of the flight recorders will take place in the shortest possible time,” Brazil's air force said.

Azerbaijani President Ilham Aliyev has said that that the aircraft was hit by fire from the ground over Russia and was rendered uncontrollable by electronic warfare. He accused Russia of trying to “hush up” the issue for several days.

Russian President Vladimir Putin apologized to his counterpart for what he called a “tragic incident”, but stopped short of acknowledging that Moscow was responsible.

Putin’s apology to President Ilham Aliyev came as allegations mounted that the plane had been shot down by Russian air defense systems attempting to fend off a Ukrainian drone strike near Grozny, the regional capital of the Russian republic of Chechnya, where the plane was heading.