Eleven juveniles and one adult were arrested Saturday after allegedly causing a disturbance in the Gold Coast neighborhood of Chicago, police said.
The group of 40 to 60 teens was seen disrupting and running through traffic along North Michigan Avenue, according to police.
The disturbance came on the same day Governor Quinn signed into law new legislation that would implement harsher penalties for violent flash mobs who organize via social media.
A heavy police presence flocked to the scene and began ushering the group onto the CTA's Red Line.
Twelve teens were arrested and charged with obstructing traffic and being reckless, police said.
The incident was considered a "minor disturbance" and no injuries were reported, according to police.
Recent attacks along the Magnificent Mile prompted concerns from many area residents.
Last month, more than two dozen teens were arrested after groups began randomly attacking each other and pedestrians along Chicago’s Magnificent Mile.
"We see it virtually every year when the weather gets warm,” Supt. Garry McCarthy said after last month's attacks.