Metropolitan Police detectives arrested 13 people ahead of the Brixton Splash festival in London on suspicion of drug dealing and imprisoning two 15-year-old girls.
Officers executed 19 search warrants at addresses in Croydon, Lambeth, Southwark and Wandsworth before the street festival kicked off on Sunday (2 August).
Those arrested were for various offences including possession of class A and B drugs with intent to supply and theft. Of those, three men were arrested at an address in Southwark on suspicion of false imprisonment.
All three currently remain in custody at a south London police station pending further enquires after two 15-year-old girls were found at the address.
Specialist officers from the Sexual Offences, Exploitation and Child Abuse Command are providing assistance to the investigation.
As part of the pre-planned activity in the lead-up to today's community event, weapon sweeps were carried out in Acre Lane, Electric Avenue, and Windrush Square. Officers recovered a six inch (15cm) knife in Windrush Square and this will now be subject to forensic examination.
Started in 2005, Brixton Splash is a community street festival in the heart of the south London district attracting more than 20,000 people throughout the day.
Detective Chief Inspector Jim Redmond from Lambeth borough said: "Brixton Splash is a family event held by the local community and whilst we did not have specific intelligence that those arrested would attend today we have undertaken this morning's activity to deter those who may have had plans to come and disrupt the event.
"A number of arrests have been made and this should send a clear message that this type of crime will not be tolerated.
"Police will be supporting the organisers and stewards in the delivery of a safe event to ensure that those attending are able to enjoy today without worrying about crime and violence."