EMBED >More News Videos Police said the teens gathered near Red Line stop at 800 North state where they were reportedly fighting amongst themselves, trespassing, and refusing to listen to officers.

CHICAGO (WLS) -- Chicago police arrested more than a dozen young people downtown Sunday, after officers say large groups of teens started causing problems.Police said the teens gathered near Red Line stop at 800 North State Street, where they were reportedly fighting amongst themselves, trespassing, and refusing to listen to officers.Police increased patrols this weekend downtown after a similar situation Wednesday night when hundreds of teens flooded into Millennium Park.Thirty-one people were arrested in the first incident and are facing charges that include disorderly mob action, resisting arrest and battery.No one was seriously injured in the disturbance, but the Chicago Police Department issued a warning ahead of summer that this behavior won't be tolerated.