ST. PAUL, Minn.  On the weekend before the Republican National Convention, law enforcement agencies detained dozens of people and issued a series of search warrants aimed at groups believed to be organizing demonstrations while delegates and Republican officials are in town.

On Friday night the Ramsey County sheriff's department, accompanied by the St. Paul police, detained people inside a building here that was being used as a headquarters to plan protests.

“They handcuffed all of us,” said Sonia Silbert, 28, from Washington. “They searched everyone.”

People who had been in the building said that officers entered shortly after 8:30 p.m. with a warrant and instructed them to lie on the ground, adding that they had been questioned and photographed before being released.

Jordan Kushner, a member of the National Lawyers Guild, said the two-story brick building had been rented by a nonprofit organization and was being used by several groups planning protests.