MOSCOW (REUTERS) - Russian investigators on Monday (March 21) were trying to restore the damaged cockpit voice recorder of a passenger jet which crashed at the weekend killing all 62 people onboard, in an effort to understand why it had tried to land in strong winds.

The Boeing 737-800, operated by Dubai-based budget carrier Flydubai, crashed in the early hours of Saturday at Rostov-on-Don airport in southern Russia in strong, gusting winds on its second attempt to land.

The stricken plane's flight data recorder survived largely intact, but the cockpit voice recorder - which should shed crucial light on the pilots' final conversations before the crash - was badly damaged and needs to be restored.

That process could take weeks, officials have said.

There is so far no suggestion of terrorism.

Russian media say the two main theories under consideration by investigators, who have opened a criminal investigation into the tragedy, are possible pilot error or a technical failure.

Flydubai's CEO Ghaith al-Ghaith said on Saturday it was too early to determine why the plane, which was just over five years old, crashed.

One of the big unanswered questions is why the plane attempted to land in what were reported to be fiercely strong winds and did not divert to a nearby airport. An Aeroflot plane had earlier made several aborted landing attempts and been diverted.

Investigators are likely to focus, among other issues, on how the decision to land was reached, why the plane circled above the airport in a holding pattern for over two hours, and on the precise thinking of the pilots and the airport's landing tower.