The two groups on Monday night indulged in arguments and pelted each other with stones, following which the police lobbed teargas shells to disperse them, they said. Later, Additional District Magistrate Neha Meena ordered the imposition of the Criminal Procedure Code (CrPC) Section 144 (prohibiting gathering of five or more people) in the Neemuch city police station limits. Four cases were registered, and nine people rounded up so far, Neemuch's Superintendent of Police Suraj Kumar Verma told reporters, adding that a police officer suffered a knee injury.