A 13-year-old girl was sexually assaulted by a gang of youths.
Detectives from the Sexual Offences Exploitation and Child Abuse Command are investigating an attack on the teenager on Sunday afternoon.
She was assaulted by a group of youths in a block of flats in Essex Road and then again in Stoneydown Park in Walthamstow.
The incident happened sometime between 5pm and 9pm.
A police cordon was set up around the park yesterday morning at around 7am and remained in place late into the evening.
Entrances to the park in Pretoria Avenue and Blackhorse Road were taped off, with an officer guarding each entrance.
The park, used frequently by schoolchildren, borders Stoneydown Primary School and Nursery in Pretoria Avenue and St Patrick's Catholic Primary School in Longfield Avenue.
It remains taped off and closed to the public but officers are no longer guarding the park.
No arrests have been made.
People living nearby said there are regular problems in the park.
A 35-year-old mother, who lives opposite the park in Lloyd Road, did not want to be named because of the threat of gangs.
She said: “Sadly, I’m not surprised. There are too many underage kids drinking and smoking in the park and they congregate their late at night.”
A 25-year-old off licence owner in Blackhorse Road also asked not to be named.
He said: “There is always misbehaviour. The park is never clean and rather than to try to resolve these problems, the police don’t bother until the crime actually happens.”
Police are urgently appealing for anyone with information to contact the incident room on 0208 217 6541 or call Crimestoppers anonymously on 0800 555 111.