MOSCOW (AP) _ A passenger bus plunged off a ferry into a river in central Russia on Sunday, killing 13 people, emergency officials said.

The bus, traveling a standard route from the regional capital Kazan to the town of Bazarniye Mataki, had just driven onto the ferry's deck when it rolled into the Kama River, said Sergei Klevakin, chief spokesman for the Emergencies Ministry branch in the province of Tatarstan.

The cause of the accident was unclear.

Rescuers saved the bus driver and one passenger, but all the others aboard were killed, Klevakin said. He had no details about the victims.