TBILISI, Georgia (AP) _ A passenger bus drove off a rocky mountain road and plunged into a river in western Georgia, killing at least 23 people and injuring 18.

The bus crashed into the Rioni River after leaving the road and falling 80 yards near the mountain city of Ambrolauri on Sunday evening, the ITAR-Tass news agency reported today.

``The bus driver failed to drive the vehicle (properly) on the rocky road. It looks like his mistake,'' Interior Ministry spokesman Valiko Gogolashvili said.

The city of Ambrolauri is about 220 miles west of the Georgian capital Tbilisi.