Protests live updates: Marines make 1st temporary detention in LA

The Federal Bureau of Investigation has identified a man who is wanted for throwing rocks at police and law enforcement vehicles during the protest in Paramount, California, on Saturday.

The suspect has been identified as 40-year-old Elpidio Reyna, from nearby Compton, and is wanted for assault on a federal officer, according to the FBI

The FBI is offering a reward of up to $50,000 for information about the suspect, leading to his arrest and conviction.

The incident happened at approximately 3:30 p.m. on Saturday, according to the FBI, when the suspect threw rocks at law enforcement vehicles on Alondra Boulevard in Paramount, injuring a federal officer and damaging government vehicles.

As the immigration protests in Los Angeles continue, demonstrations were also seen in New York City, Austin, Texas, and just south of L.A. in Santa Ana, California.

The number of National Guard troops on the ground in the Los Angeles area has risen from 300 to 1,700, the Defense Department said in an update Monday evening.

The guardsmen are from the 79th Infantry Brigade Combat Team, a California National Guard unit. They are operating under Task Force 51, which also includes 700 Marines, to protect federal personnel and property, U.S. NORTHCOM said in a statement.

President Donald Trump's memo over the weekend authorized a deployment of 2,000 National Guardsmen amid unrest during protests over immigration enforcement in the LA area.

California Gov. Gavin Newsom said Monday he had been informed Trump planned to deploy an additional 2,000 National Guard troops.

Protests on Monday saw police slowly, methodically build up a massive presence outside of Los Angeles' federal buildings.

On the bullhorn, an officer was heard warning protesters -- who appeared to be angling to get back to the 101 Freeway and who had commandeered Los Angeles Street -- that they'd have five minutes to disperse the unlawful assembly.

An hour later, they still hadn't moved on the protesters who were jeering and taunting them, but behind them, Los Angeles Sheriff's SWAT teams had moved into the scene in armored cars with sound cannons and portable barriers. LAPD Cruisers and Suburbans closed ranks behind them, effectively sealing the street.

They moved as if in a brigade-sized military exercise, taking the high ground of the garage -- flooding the lower floors with officers then and pouring in from alleys and side streets. It was a pincer movement that sent some of the protesters scattering. They fired lots of less lethal rounds and flash bangs thundered. Everyone moved back.

Los Angeles' Temple Street had dozens of cruisers and hundreds of officers. Dozens of additional cruisers were also seen on Alameda Street with hundreds of officers.

-ABC News' Matt Gutman and Timmy Truong