The New York Police Department has activated its Joint Operations Center in coordination with FBI, state, local and federal partners ahead of what is expected to be widespread protests Saturday across the city.

Some 34,000 members of the NYPD will be on the streets of New York City over the next 24 hours.

"You do not have a right to engage in violence and lawlessness," Mayor Eric Adams said in a news conference yesterday ahead of the planned protests.

United States Army North confirmed to ABC News that Marines at the Wilshire Federal Building have made the first temporary detention among the troops sent to Los Angeles on Friday.

In an interview earlier in the week, Maj. Gen. Scott Sherman -- the commander of Joint Task Force 51 -- said, "We're there to protect their federal officers, their federal personnel.”

If those personnel are assaulted, Sherman said, "Soldiers or Marines are allowed to take that person, detain them in place, wait for the federal law enforcement officer to come and arrest that individual."

It was not immediately clear what led to the detainment on Friday.

-ABC News' Luis Martinez

About 200 Marines are taking over responsibility for protecting the Wilshire Federal Building in Los Angeles, Maj. Gen. Scott Sherman told reporters Friday.

The addition of those troops will allow more National Guardsmen to be trained to accompany federal personnel during Immigration and Customs Enforcement raids, according to Sherman.

“The soldiers that were performing those duties will then transition to providing protection to federal law enforcement officers as they conduct their law enforcement function,” Sherman said. “I would like to emphasize that the soldiers will not participate in law enforcement activities. Rather, they'll be focused on protecting federal law enforcement personnel."

Sherman serves as the commander of Joint Task Force 51, the command headquarters for the 4,000 federalized National Guardsmen and 700 Marines assigned to protect federal personnel and property in Los Angeles.

In an interview with ABC and the Associated Press earlier this week, Sherman said, as of then, about 500 of the 4,000 National Guardsmen assigned to the LA area had been specifically trained to work with ICE teams.

-ABC News' Luis Martinez

Marines are now on duty in Los Angeles for the first time. Some were spotted guarding the Wilshire Federal Building on Friday.

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