Apparently responding to a social media messages, hundreds of teenagers and young adults massed in North Philadelphia late Sunday and some in the roving crowds turned unruly, damaging at least six police cars.

No arrests and no injuries were reported after the crowds dispersed early Monday.

Police Commissioner Richard Ross told reporters are Police Headquarters Monday morning that 600 to 800 people gathered in the area of Sydenham and Jefferson Streets about 11:30 p.m. and that most in the crowds were peaceful.

Still, some blocked intersections and others damaged patrol cars after police moved in to disperse the crowds.

Police said at least six police cars sustained damage, including smashed windshields, dented hoods, trunks and roofs and ripped out door mirrors.

“We don’t know why they gathered. We don’t know whether there was a party," Chief Inspector Joel Dales told reporters at the scene Sunday night. "We have no information whatsoever giving us a warning that these kids were going to gather out here.”

Ross said Monday morning that it appeared word of a large cookout on Instagram triggered the mass gathering, 6ABC reported.