The operation was the largest of its kind and resulted in the arrests of illegal immigrants convicted of robbery, assault and rape, said John Morton, head of U.S. Immigration and Customs Enforcement. The sweep ended Thursday night. Ninety-six of the 286 arrests took place in Los Angeles County. Among those arrested in the county were a suspected gang member from El Salvador who had a 2004 robbery conviction and a Guatemalan man with a 1993 conviction for lewd acts with a child under 14. 'These are not people we want walking our streets,' Morton said. The arrests were conducted as part of a controversial program designed to arrest and deport immigrants who have criminal records, who have ignored deportation orders or who have been deported and illegally re-entered the United States. About 400 officers and agents took part in the operation. The arrests included people from Mexico, Denmark, Taiwan and Tonga. Critics have said the 'fugitive operations' program, which started in 2003 and has rapidly expanded since then, has created fear in immigrant communities by sending armed agents into neighborhoods and pulling parents away from their children. To fill quotas, immigration agents also often arrested people without criminal records or outstanding deportation orders, according to a report by the Migration Policy Institute earlier this year. During a visit to Los Angeles over the summer, Morton announced that he would end the quotas. Only six people arrested in the operation this week did not have criminal records, he said. On Friday, Morton said the agency is enforcing immigration law, but that there is a particular focus on arresting and deporting criminals, through this program and another in the jails and prisons across the nation. (Begin optional trim) 'We are an agency of limited resources,' he said. 'It makes a tremendous amount of sense for us as an agency and for the country for us to start with criminal offenders.' Angelica Salas, executive director of the Coalition for Humane Immigrant Rights of Los Angeles, said Friday the sweep demonstrates Immigration and Customs Enforcement is serious about going after convicted criminals; but she said she believed some of the crimes may have been minor and that this is not necessarily the most effective way to fight crime in the community. (End optional trim) There are 104 teams of officers nationwide who conduct such operations. More than 35,000 people were arrested by fugitive operations teams in fiscal year 2009, according to ICE. Of those, nearly 89 percent either had criminal records or outstanding deportation orders. Although some were never deported after serving time for criminal convictions, many of those arrested this week had previously been deported and returned to the United States illegally, authorities said. For example, Ulises Vazuiz Arucha, 37, was convicted of first-degree robbery in 2004 and deported to El Salvador in 2007. The suspected gang member was arrested on Dec. 8. 