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.

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 second black box has been found at the plane crash site near Aktau and handed over to the investigation department, according to a Kazakh official from transport department on Thursday. The Embraer 190 aircraft operated by Azerbaijan Airlines flight J2-8243 from Baku to Grozny crashed near Aktau Airport in Kazakhstan on Wednesday.