LOS ANGELES -- Los Angeles police have been drilling with mock protesters to prepare for Thursday's immigrant-rights demonstration in an attempt to avoid clashes like last year.

Police with "extraction units" will be trained to remove unsavory people from the crowd expected to converge on downtown as part of rallies organized by groups such as Latino Movement USA, the Los Angeles Times reported.

"Is everyone clear on chain of command?" Deputy Chief Michael Hillmann asked the officers during a recent training session in the parking lot of Dodger Stadium.

A few rowdies threw objects at police in MacArthur Park during last year's May 1 demonstration, and that led officers to sweep the park, using clubs and non-lethal firearms on stragglers and journalists who didn't move fast enough.

Some 240 protesters and journalists claimed they were hurt, as did 18 officers.

"It was probably the most significant multiple set of crises all occurring at the same time that I had ever faced in my career," police Chief Bill Bratton told The Times in a recent interview. "But in responding to them, it was always with the focus of `OK, how out of this negative can we get something positive?"'

This year's march is expected to attract from 20,000 to 100,000 people.

Protesters will gather at two sites -- Olympic Boulevard and Broadway, and at MacArthur Park, starting at 2 p.m. Both groups will start marching toward City Hall, converging at Fifth and Broadway. "It's up to the LAPD to follow through on their promise, to be there to support the march and make sure all of the march participants have a good experience," Bethany Leal of the Multi-Ethnic Immigrant Worker Organizing Network told The Times.

Juan Jose Gutierrez of Latino Movement USA said many immigrants distrust police because of the heavy-handed tactics used last year.

Federal monitors, who oversee the department's efforts to comply with a set of mandated reforms imposed after a corruption and abuse scandal in the late 1990s, will be on hand for the demonstration to observe how police handle the crowds, the newspaper reported.

An LAPD probe of events last year resulted in allegations of misconduct against 29 officers, but a discipline panel has yet to make any recommendations about punishment.

More than 250 claims were filed against the city. Attorneys from the Mexican American Legal Defense and Educational Fund and private firms are negotiating a possible settlement in the case, the newspaper reported.