COEUR D’ALENE, Idaho — Dozens of members of a white supremacist group were arrested on Saturday in Idaho before they could act on plans to riot at a local Pride event, the police said.

After receiving a tip from a concerned citizen, the police detained and charged 31 people who belonged to a far-right group known as Patriot Front, said Lee White, the chief of the Coeur d’Alene Police Department, at a news conference.

They are being charged with conspiracy to riot, a misdemeanor, he said. Bob Norris, the sheriff of Kootenai County, said that a person reported seeing a group of people jump into a U-Haul van near the intersection of Northwest Boulevard and Interstate 90 in Coeur d’Alene. “And they were all dressed like a small army,” Sheriff Norris said. “We had units in their area, and we were able to intercept them pretty quickly.” A few miles away, the North Idaho Pride Alliance was holding “Pride in the Park,” an annual event, at Coeur d’Alene City Park.