As part of a nationwide operation targeting street gangs, federal authorities arrested more than two dozen suspected gang members in the D.C. area, officials from U.S. Immigration and Customs Enforcement said Thursday.

The defendants include nine alleged members of the Mara Salvatrucha gang, known as MS-13, who were arrested in Prince George’s County on charges including murder, extortion, assault and racketeering.

More than 600 gang members and associates were arrested in cities across the U.S. during the month-long operation Project Southbound, which ran from March 12 to April 13, officials said. The operation targeted the transnational street gang Sureños, called Sur 13, and its affiliated gangs, including MS-13, 18th Street and Florencia 13.

“Transnational criminal street gang members contribute nothing good to society,” ICE official Thomas Winkowski said at the press conference. “Left unchecked, their numbers will only increase, and their violence, crime and intimidation will continue to snowball.”

Authorities said the gang members were involved in slayings, human trafficking, drug trafficking, extortion and prostitution. During the operation, Homeland Security agents seized over 50 firearms and methamphetamine, cocaine, marijuana and heroin.

Agents also arrested over 100 individuals on criminal or immigration violations.

Project Southbound was part of a 10-year effort led by HSI in cooperation with federal, state, local and foreign law enforcement partners. Winkowski said after this operation, ICE has a number of initiatives that will address MS-13.

“We believe this is just the tip of the iceberg,” Winkowski said.