Updated

The Obama administration said Monday it arrested more than 3,100 immigrants who were illegally in the country and who were convicted of serious crimes or otherwise considered fugitives or threats to national security. It was part of a six-day nationwide sweep that the government described as the largest of its kind.

U.S. Immigration and Customs Enforcement said the sweep included every state and involved more than 1,900 of the agency's officers and agents.

The sweep comes nearly a year after ICE pledged to focus on deporting illegal immigrants with serious criminal histories and those who posed national security threats, while going easier on many who stay out of trouble. The agency's director, John Morton, said the arrests underscored that focus.

"There are 3,168 fewer criminal aliens and egregious immigration law violators in our neighborhoods," Morton said.

Officials said most of those arrested had entered the country illegally. Others had violated the terms for legally being in the United States and were subject to deportation.

More than 1,000 of the people arrested had multiple criminal convictions. The most severe cases included murder, manslaughter, drug trafficking and sexual crimes against minors.

The totals included an estimated 50 gang members and 149 convicted sex offenders. The cases of at least 204 of them were referred to federal prosecutors for a variety of serious charges, including illegal re-entry after deportation, a felony that can carry up to 20 years in prison.

Morton issued guidelines in June that suggested the agency would ease up on illegal immigrants who are military veterans, elderly, in the United States since childhood or had relatives who were citizens or legal residents. In August, the Department of Homeland Security announced a review of about 300,000 cases in the nation's clogged immigration courts aimed at giving reprieves to the lowest-priority offenders.

Latinos and other immigrant communities have eyed the pledges warily as the Obama administration has removed record numbers of illegal immigrants -- nearly 400,000 in each of the last three years.

The agents participating in last week's sweeps typically knock on doors early in the morning before people go to work.

A San Diego team began Wednesday in a neighborhood of large, cookie-cutter homes, looking for a Laotian man who had convictions for burglary, assault, amphetamine possession and disorderly conduct. After 20 minutes of waiting in unmarked cars, a person emerged who told law enforcement that their target wasn't home.

From there, the agents went to a modest neighborhood in suburban Chula Vista to look for a Cuban who had convictions for involuntary manslaughter, battery, vehicle theft and spousal abuse. A resident said the man moved, and a next-door neighbor corroborated.

The third stop finally produced an arrest -- a Somali man who was on supervised release for a drug conviction. He was living at a halfway house in San Diego.

In all, the San Diego agents targeted 14 illegal immigrants and found six. They arrested six others who were not targets, increasing the day's arrest tally to 12. Lauren Mack, a spokeswoman for ICE, said the non-targets either had deportation orders or were previously removed from the United States.

The sweep included 116 different nationalities and represented the third such sweep under the program called Operation Cross Check. The last sweep resulted in the arrest of about 2,900 people.