Immigration and Customs Enforcement said Thursday that its investigative branch, along with other law enforcement agencies, has arrested 1,378 people across the United States in recent weeks in what officials called the largest anti-gang crackdown in the agency’s history.

More than two-thirds of the people arrested are U.S. citizens, and all but two of those were born in this country, ICE officials said.

The arrests were part of a six-week initiative, from March 26 to May 6, led by ICE’s Homeland Security Investigations unit, which focuses on combating gangs and other criminal activity in the United States and overseas.

Unlike the agency’s immigration section, HSI has broad powers to enforce hundreds of federal laws on crimes such as child exploitation, human smuggling, and drug and weapons trafficking. Its agents routinely arrest U.S. citizens.