More than 600 people have signed a petition against Metro’s new random bag searching policy.

The D.C. Bill of Rights Coalition and the Montgomery County Civil Rights Coalition have been gathering signatures since the transit agency began checkpoints to randomly screen riders’ belongings for explosives late last month.

The two civil liberties groups argue that such searches violate the Fourth Amendment. So far, 646 people and counting agree with them, said Pat Elder, a co-founder of the D.C. group.

The group plans to present the signatures to Metro’s Riders’ Advisory Council Monday night at a public forum on the searches.

The groups opposed a similar policy proposal two years ago and Metro backed down, never starting the bag inspections. The groups are hoping for a repeat response.