At least 42 people have been killed and nine people hurt in a collision between a train and a small bus in eastern Ukraine, officials say.
The incident happened near the town of Marhanets, south of the main regional city of Dnipropetrovsk.
The inter-city passenger bus tried to cross the track, ignoring the warning of an approaching train, reports said.
Some of the injured are in a critical condition and the death toll could rise.
Railway officials said all the casualties were on the bus.
The ministry of the interior said the train had dragged the bus for 30 metres after the collision.
"The driver of the bus broke traffic laws by driving through a red light before colliding with the train," a spokeswoman for the regional traffic police told the Agence France-Presse news agency.
"It's utter carnage there."
The Transport Minister Kostyantyn Yefymenko is quoted in several Ukrainian news agencies recounting what survivors have already been saying to investigators.
"The bus was standing still," said Mr Yefymenko, "and the driver was standing near the bus, then he got in and started driving right before the locomotive."
This, he said, was despite passengers warning the driver that the alarm lights were flashing.
President Viktor Yanukovych has ordered law enforcement agencies to carry out a detailed investigation to establish who was responsible for the accident.
But the Prime Minister Mykola Azarov said he thought authorities should install automatic crossing gates anyway.
"It is not worth saving on human lives," said Mr Azarov.
Ukraine has a bad safety record due to the poor condition of many roads and drivers who regularly flout the rules.
The president conveyed his condolences to the relatives of the victims and has declared Wednesday a national day of mourning.