Metropolitan Police say the girl was taken from Galliard Road into Jubilee Park, Lower Edmonton, Enfield, on her way home at about 5pm London time on Friday.
Police have revealed the attack could have lasted as long as three hours and resulted in serious injuries to the girl.
An 18-year-old was arrested in Edmonton on Monday night is being held in a police station in London’s north-east.
A 26-year-old man, who was held earlier on Monday, was bailed until late December.
Police report the girl caught the number 192 bus from Enfield Town at 4.15pm and disembarked in Bury Street before walk home on Galliard Road when she was attacked. The victim returned home at about 7.45pm that night.
She is recovering after surgery for her injuries.