Anti-frac sand protesters delayed a tour bus from taking a field trip to mining and processing sites in western Wisconsin today by climbing onto the vehicle's roof and hiding the ladder that they used to get there.

The seven Catholic Worker volunteers from Winona and Des Moines, Iowa, were arrested by police in Brooklyn Center, Minn., after more than 90 minutes atop the bus. They were cited for unlawful assembly, booked and released.

It was the second protest in three days outside the Conference on the Silica Sand Resources of Minnesota and Wisconsin at Earle Brown Heritage Center.

The protesters unfurled a banner over the windshield of the bus that read "Our tragedy is not your tour."

Photo courtesy Jake Olzen