REUTERS/Lucy Nicholson

Over 240 undocumented immigrants were taken into federal custody in Southern California after a four-day immigration sweep rounded up individuals with criminal records, US Immigration and Customs Enforcement (Ice) officials announced on 31 August.

According to a statement released by the agency, 56% of those taken into custody had criminal records including felony convictions for child sex crimes, weapons charges, drug violations and other series offences.

Ice revealed that a majority of the undocumented immigrants taken into custody were originally from Mexico—191 immigrants—but noted that 21 countries were represented overall.

"The foreign nationals detained during the enforcement action who are not being criminally prosecuted will be processed administratively for removal from the United States," the statement said.

Agency spokeswoman Virginia Kice told the Los Angeles Times: "One of the challenges we're facing is because of state law and local policies, more individuals who are potentially deportable with significant criminal histories are being released onto the street instead of being turned over to Ice .... I think to infer from [the sweep] that potentially foreign nationals are committing more crimes is flawed."

Ice noted that not all those captured in the sweep were in the US illegally. Some of the documented immigrants will be deported due to recent crimes. According to the LA Times, the agency used to contact local jails to pick up immigrants who had been arrested. However, a federal judge ruled last year that the practice was illegal.

Not all the immigrants arrested had previous violent criminal records. The LA Times reported that those who had not been deported previously and had been found to have illegally re-entered the US or are not facing new charges will have an administrative hearing with a judge.