DENVER — The American Civil Liberties Union in Colorado is suing federal immigration officials on behalf of a Brazilian immigrant in Utah and several others, saying their arrests underscore what the civil rights group believes to be “illegal and discriminatory” behavior by immigration authorities.

The experiences of Caroline Dias Goncalves and three others singled out in the lawsuit “are not unique,” it reads. “They reflect an unlawful practice that immigration officers rely on in their enforcement operations across the country and throughout Colorado: Make warrantless arrests without the requisite probable cause determinations regarding legal status and flight risk.”

The lawsuit , filed Oct. 9 in U.S. District Court in Denver, asks the court to order immigration authorities to halt such

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