Russian investigators were this morning combing through the charred fragments of a Boeing 737 jetliner as they tried to determine what caused a crash that killed all 50 people on board.
The Tatarstan Airlines plane crashed on Sunday while trying to land at its home port in the Russian city of Kazan, the capital of the oil-rich province of Tatarstan. The son of the provincial governor and the chief of the local branch of Russia's main security agency were among the victims.
The plane crashed while making a second attempt at landing, said Alexander Poltinin, the head of the local branch of Russia's Investigative Committee.
Mr Poltinin said investigators are looking into possible pilot error or equipment failure.
The traffic controller at the Kazan airport, who contacted the plane before the crash, said the crew told him they weren't ready for landing, but did not specify the problem.
The plane exploded on impact. Mr Poltinin said it could take weeks to identify the victims. Russian emergency ministry officials said a British national, Donna Bull, was among the victims.
The investigators have found both of the plane's black boxes, which contain the recording of its systems performance and the crew conversations.
Magomed Tolboyev, a highly decorated Russian test pilot, said on Rossiya television that it wasn't immediately clear why the crew was unable to land at first try in good weather, saying it could be linked to a failure of some of the plane's systems or crew error.
The plane that crashed was built 23 years ago and had seen service with several carriers prior to being commissioned by Tatarstan Airlines. The company insisted the aircraft was in good technical condition.
The carrier has had a good safety record, but appears to have run into financial problems recently. Its personnel went on strike in September over back wages, and the Kazan airport authority has gone to arbitration to claim what it said was Tatarstan Airlines' debt for servicing its planes.