Prince William County has unanimously approved a measure aimed at discouraging illegal immigrants from settling in the northern Virginia county.

Hundreds of people packed a meeting Tuesday before the eight-member Board of Supervisors voted on the proposal.

It requires county police to check on the immigration status of anyone they detain if there is probable cause to believe the person is undocumented.

It would also permit other county workers to ensure people are in the country legally before providing services.

After the vote, opponents of the measure rallied outside, promising to fight it.

Immigrant rights advocates fear the intent is to deny a wide range of services, including medical care, library access and even the federally protected right to schooling. They say that will inevitably lead to racial discrimination.