An Arizona sherriff's office is under investigation after activists alleged it violated the civil rights of illegal immigrants.

The Department of Justice began investigating the Maricopa County Sheriff's Office at the request of Congressmen John Conyers (D-Mich.), Jerrold Nadler (D-N.Y.), Zoe Lofgren (D-Calif.), and Robert Scott (D-Va.), as well as activist groups such as National Day Laborer Organizer Network and ACORN, according to CNSNews.com.

The probe will examine Sheriff Joe Arpaio and dozens of his officers trained in Immigration and Customs Enforcement’s Agreements of Cooperation in Communities to Enhance Safety and Security program, which joins federal and local law authorities to enforce immigration laws, CNSNews.com reported.

The department will focus on "alleged patterns or practices of discriminatory police practices and unconstitutional searches and seizures conducted by the MCSO and on allegations of national origin discrimination, including failure to provide meaningful access to MCSO services for limited English proficient (LEP) individuals," according to a letter from Loretta Smith, the Justice Department's acting assistant attorney general.

Sheriff Arpaio's has been criticized in the past for his immigration law enforcement tactics. He defended his department and its results, telling CNSNews.com, "What I am doing is upholding the laws of the state of Arizona, and I will not be persuaded to turn my back on my oath of office as sheriff of this county."

The Democratic Congress is also calling for an investigation into the ICE training program.

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