Authorities said another 151 people were prevented from reaching the site after a planned police swoop on organised gangs gathering at the Oval, south London.
Edwards said officers acted on information to confront the gangs at 4.20pm yesterday. "We had intelligence to suggest that people at the Oval were from a variety of gangs and that they were on their way to the carnival to commit crime, engage in disorder and potentially violence," she said.
"Some members were arrested for substantial offences such as possession of weapons. Others were detained to prevent a further breach of the peace."
Edwards said teams of specialist dog handlers worked with the RSPCA to seize 21 dangerous dogs taken to the carnival in response to concerns raised after last year's event.