Two persons were killed and 45 policemen injured in the violence that erupted after a rally organised by city-based Raza Academy in the afternoon at Azad Maidan in South Mumbai turned unruly, with the mob damaging buses, hurling stones and setting vehicles on fire.
The rally was being held to denounce riots in Assam and also the alleged attacks on a minority community in Myanmar.
"The police could have used more force but the fact that 45 policemen were among the injured proves that they did everything possible to control the mob," Chavan told reporters at the state government's Sahyadri Guest House at Malabar Hill.
"The police used lathi-charge, tear gas and rubber bullets to disperse the violent crowd and in the end fired in which two persons were killed," he said.
On the mandate given to the crime branch to probe the incident, Chavan said, "The investigation will explore the possibility whether it was a preplanned act and also delve into conspiracy angle, if any."
Replying to a query on any arrests made in the wake of the violence, Chavan said "some" people have been taken into custody for questioning.
On the security scenario, the chief minister said, "Police bandobast has been stepped up in the city and state and 18 platoons of para-military forces have been deployed."
Home Minister R R Patil who was also present at the briefing said those behind the violence will not be spared.
"There was no lack of coordination among police force," Patil said in reply to a query.