Four policemen, one bus passenger and a bus driver were injured in the scuffle that followed after a civic police volunteer personnel beat the bus driver when he violated traffic rules, police said.
A passenger seated behind the bus driver was also injured, bus operators claimed.
Later, angry bus operators damaged one booth of the traffic policemen near Howrah station.
Four bus operators were detained for causing inconvenience to the people and blocking the main road, the police said.