The bus which was going to Karachi fell into a ravine in Lak Pass area near provincial capital Quetta, when the driver lost control of the bus while overtaking another vehicle.
The injured are transferred to various hospitals in Quetta, police said.
Provincial Chief Minister Nawab Sanaullah Khan Zehri has announced financial aid for the injured and relatives of the victims.
Road accidents are common in Pakistan which are often caused due to bad roads or careless driving practices.
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