Less than a day after Minneapolis police used pepper spray to disperse hundreds of youths who swarmed the city’s annual St. Patrick’s Day parade, local officials sought to reassure the public that downtown remains a safe place to be.

“Multiple fights broke out internally among the group of kids along the downtown corridor — luckily there were no serious injuries,” Mayor Betsy Hodges said in a statement posted on Facebook Wednesday. “The fights and large group of kids shut down traffic in some spots, but there was no threat to the general public at any time.”

Like many so-called flash mobs, this one materialized in a matter of hours via text and social media on Tuesday, officials said. Sometime after 8 p.m., more than 300 young people, some taking advantage of free rides on Metro Transit buses and trains, converged on downtown, catching authorities off guard.

Most of the crowds had been dispersed shortly after 10 p.m.

Police Chief Janeé Harteau said her officers, some of whom used pepper spray on the roving groups of youths, did an “incredible job of exercising restraint.”

Similar so-called “bash mobs” have materialized in recent years in cities like Philadelphia, Chicago and Los Angeles, raising questions about whether those who send out tweets should be held responsible for the problems they cause.

“A lot of St. Patrick’s Day stuff revolves around the celebratory party. This crowd here, they kinda wanted to run through the crowds,” causing havoc, said First Precinct Inspector Mike Kjos.