(Adds details, possible cause)

MOSCOW, March 26 (Reuters) - Fourteen people died and four were injured on Thursday when a bus burst into flames after colliding with a lorry just east of Moscow, Russia's Emergency Ministry said.

Rescue workers used a crane to peel the blackened roof from the twisted metal frame of the bus on the outskirts of Petushki, a small town located about 100 km (60 miles) east of Moscow, television pictures showed.

Local media reported most of the victims were traders travelling to a Moscow market from the city of Ulyanovsk, 800 km (500 miles) east of the capital.

"According to our latest information, 14 people died -- the driver of the truck and 13 people on the bus," Emergency Ministry spokeswoman Lyudmila Martynova said.

Casualty numbers could change due to the difficulty of identifying remains from the burnt-out bus, she said. Local news reports earlier said 25 people had died in the accident.

There were different reports about the cause of the accident, with some officials saying one of the truck's tyres had blown out while the head of the local traffic police said the truck driver had fallen asleep at the wheel.

Russia's overloaded roads are treacherous with many drivers giving scant attention to even basic traffic safety rules. About 30,000 people died in Russian road accidents last year. (Writing by Conor Humphries and Guy Faulconbridge, editing by Richard Williams)

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