"We had intelligence inputs that there would be about 20,000 people during the demonstration and possibility of some trouble at that place..., That was the reason why a joint police commissioner, additional police commissioner and four deputy police commissioners were deployed with over 700 men in uniform," Patnaik said.
Because of these inputs, the fast worsening situation could be contained by police in just 35 minutes, he said.
The city police chief said a Special Investigating Team (SIT) has been formed to probe the violence while a magisterial inquiry has been ordered to look into the police firing and how the situation went out of control.
Patnaik was speaking to media after holding a meeting with police officers on security issues arising out of the August 11 incident, the upcoming festival season and the two-day scheduled visit of Prime Minister Manmohan Singh beginning from August 17.
According to an officer, the prime minister is likely to visit the site of violence in South Mumbai.
Two youths were killed and at least 52 people, including 44 policemen, were injured when a protest being held at Azad Maidan to condemn Assam riots turned violent, with protesters going on a rampage by torching vehicles, pelting stones and damaging buses, forcing police to fire in the air and use batons to disperse the unruly mob.
Explaining the Saturday's course of events, the police commissioner said, "There were some groups outside the Azad Maidan ground which triggered the violence first and not the 20,000 demonstrators.
"Within six to seven minutes, the unruly mob torched some vehicles and attacked police vans. When I learnt about it after speaking to my colleague, I immediately rushed to the spot and contained the situation," Patnaik said.