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By 10pm the group had started lighting fires around the police building, local news reported.
One fire had been lit behind the building, people shot fireworks towards the office and others appeared to use accelerants on a door to ignite another blaze, police said.
A riot was declared about 10 minutes after the group arrived at the building, with police saying they arrested one person.
Firefighters quickly arrived at the scene and were able to extinguish the blaze.
In Minnesota more than 60 people were arrested on Tuesday night, State Patrol Colonel Matt Langer told reporters, after hundreds protesters gathered outside the Brooklyn Center police headquarters.