Niagara Regional Police say several thousand people pushed through the fences at a free Billy Talent concert in Port Colborne, Ont., on Saturday.
Municipal officials say the venue at H. H. Knoll Park had reached capacity just before 9:30 p.m., at which point police decided to close the surrounding fences.
Police say in a statement today that a crowd of about 4,000 to 5,000 people outside the fences then pushed through the perimeter, challenging officers and security guards and leaving one officer with minor injuries.
The City of Port Colborne says about 15 minor injuries were reported among the concertgoers, and organizers decided to shut down alcohol service in the interest of public safety.
An estimated 25,000 people showed up at the small venue, more than double the 10,000 expected.
Police say it was decided to let the concert continue after consulting with members of Billy Talent.
The mayor of Port Colborne, William Steele, said he was "deeply disappointed" with those who rushed the fences but expressed gratitude for the support of event staff and volunteers as well as the response from police and security services.
The show was part a free, three-day festival called Canal Days.
