Hundreds of federal and local law enforcement fanned out across Los Angeles in pre-dawn sweeps, serving arrest and search warrants as part of a three-year investigation into the ultra-violent street gang MS-13.

Federal prosecutors unsealed a sweeping indictment Wednesday morning charging dozens of members and leaders of the brutal street gang with a variety of crimes, including murder.

Acting U.S. Attorney Sandra Brown said the 127-page anti-racketeering indictment targets 44 members and associates of the gang, including the one-time leader of a Los Angeles faction of MS-13. Three people accused of murder could face the death penalty, she said.

Twenty-one people named in the indictment were arrested in pre-dawn raids across Los Angeles and Brown said warrants were served at more than 50 locations. Jail officials around the region also conducted cell searches, as some of those indicted were already in custody on unrelated charges. About a dozen of those arrested were so-called “shot callers” for the gang. At least three people were still at large Wednesday.

“It’s one of the largest and most entrenched gangs in Los Angeles,” Brown said. “Today’s actions will deal a critical blow to the top leadership.”

Brown said MS-13 is responsible for murders of rival gang members, drug and human trafficking, prostitution and illegal alcohol sales, among other crimes. She described the racketeering case as one of the largest single cases targeting MS-13, a gang that started in Los Angeles but has expanded to nearly every state and El Salvador. The gang is blamed for horrific violence that has sent Salvadoran immigrants fleeing that country for the United States.

Because of the group’s propensity for violence, federal and local agencies used tactical and SWAT teams to serve some of the warrants, including at a storefront along a strip of dilapidated buildings near downtown that the Bureau of Alcohol, Tobacco, Firearms and Explosives said was being used as a “casita,” or sort of club house, for one group of gang members.

Just before 4 a.m., heavily armed ATF agents raided the building and found at least seven people locked in a room. FBI Assistant Director in Charge Deirdre Fike said investigators are trying to determine if those people are human trafficking victims.

As the agents made their way through the building, they described over a police radio a labyrinth of walls and secreted rooms, something that made clearing the building time consuming

The raids and the indictment are part of a multi-agency case led by the FBI that started in 2014. More than half of those arrested and charged in the case are in the country illegally, Fike said. It was unclear how long they had been in the United States or what countries they are from.

Los Angeles Police Chief Charlie Beck and others said the suspects’ immigration status was of little consequence, given the nature of the criminal charges.

“These are criminals. Regardless of their immigration status they are going to go to prison,” Beck said. “If they ever get out…their immigration status may become an issue, but it has nothing to do with their arrest today.”

The chief said this latest indictment and raid marks the seventh time that local, state and federal authorities have targeted MS-13 and its leadership. That law enforcement pressure, he said, has led to a steady decline in the gang’s influence in the Los Angeles area. In 2012 and 2014, his department ranked the group as the number one street gang in the area, but the group has since dropped to seventh, Beck said.

There are currently about 800 known MS-13 members in the city, down from a peak of about 1,200 in recent years.

Beck said the indictment and arrests may not dismantle the gang, but they will have significant impact on its power structure, as have previous busts.

MS-13 has become a primary target of the Justice and Homeland Security departments amid the Trump administration’s broader effort to crack down on illegal immigration and violent crime. President Donald Trump and members of his administration have repeatedly said MS-13 poses a particular risk to American communities and is among the most ruthless street gangs.

Trump signed an executive order in February specifically directing federal law enforcement to focus resources on combating street gangs and transnational criminal organizations.

MS-13 leaders in El Salvador were targeted for financial sanctions by the Obama administration in 2012 as part of an earlier executive order targeting such groups.

(AP)