Los Angeles Mayor Antonio Villaraigosa called on Wednesday for an "immediate and transparent " probe into the conduct of police officers who fired rubber bullets at protestors.
Police, clad in riot gear, clashed with pro-immigration protestors during a rally on Tuesday, during which 15 police officers and at least 10 people were hurt.
Police reportedly fired rubber bullets and tear gas at the protestors, but police said the confrontation was sparked when some demonstrators threw food and bottles at officers.
Villaraigosa called the melee "a sad end to a very peaceful and positive day."
Villaraigosa asked police chief William Bratton to oversee the internal investigation.
"Some of what I've seen as chief of the department does not look appropriate," Bratton said. "There were some scenes there, clearly, based on my years of experience and the years of experience of many of my command staff, did not appear to be ( appropriate)."
Tuesday's rally by thousands of people calling for a path to citizenship for illegal immigrants was peaceful until about 6 p.m., when police tried to disperse some demonstrators who had moved off the sidewalk into Alvarado Street in downtown.
Some demonstrators responded by throwing plastic bottles and rocks at officers, police said. Several dozen riot police, clad in helmets and carrying batons, started firing a few dozen volleys of foam bullets into the crowd.
Villaraigosa said he believed those who instigated the conflict were not directly connected to the demonstrators.
Meanwhile, City Council members also decried the police conduct.
"It's very disconcerting to see what happened last night, knowing that there were children, there were families, there were folks out there trying to give an American message, a message that says all communities should be treated with respect," said Councilman Ed Reyes.
Councilman Herb Wesson said news footage of the skirmish reminded him of confrontations between police and civil rights protestors in the South during the 1960s.
Also on Wednesday, the Radio and Television News Association condemned the "violent treatment of journalists" by Los Angeles police during disturbances at the pro-immigration rally.
"The Radio and Television News Association calls for an immediate and complete investigation of the violent treatment of journalists by Los Angeles Police Department personnel at the conclusion of Tuesday's immigration march," the group said in a statement.
"There is evidence that officers knocked reporters to the ground, used batons on photographers and damaged cameras, possibly motivated by anger over journalists photographing efforts by officers to control the movements of marchers," said the statement.