Bulgarian doctors identified a ninth body on Tuesday after a fire last week swept through two sleeping carriages on a train in the worst railway incident in the Balkan country since 1992, officials said.

The incident, which was initially reported to have killed eight people, provoked a heated debate about safety standards at state railway company BDZ and prompted calls for the transport minister to resign.

"Last week, we received eight badly burnt bodies and tiny remains of a suspected ninth body, which were mixed with animal remains. We confirmed today it was a human body," said Petko Lisaev, head of the forensic unit of Pleven Medical University.

Sixty-two people were in the two coaches when the fire broke out last Thursday as the train travelled from the capital Sofia to the northern town of Kardam.

The cause of the fire was remains unknown and prosecutors and police are continuing to investigate.

Some survivors said the train lacked enough working fire-extinguishers and that railway workers failed to unlock some carriage doors.

BDZ head Oleg Petkov has defended railway safety standards and said initial investigations showed railway staff had acted professionally.

But opposition parties said the government had neglected train safety at BDZ and called for Transport Minister Petar Mutafchiev to resign.

The number of passengers served by the ailing state railway operator has dropped to about 35 million a year from over 110 million in the early 1990s, mainly due to declining quality.

The last big railway incident in the Balkan country was in August 1992, when 10 passengers died after their train collided with a cargo train.