A 14-year-old girl has been charged after police were attacked with rocks and bottles at an out of control party in Girrawheen on Friday night.
Officers were called to Templeton Crescent after groups of teens spilled out of a house and onto the street drinking and fighting.
About 120 juveniles, aged between 16 and 18, were at the party and groups of them confronted police when they arrived.
Officers were pelted with bottles and stones but no-one was hurt.
Twenty teenagers were detained under the Children's Act - four were released to a responsible adult and 16 were taken to a special 'Youth at Risk" facility.
Four people including two teenagers have been charged.
One of them is the 14-year-old girl who organised the party.
The others are a 32-year-old Girrawheen woman, a 37-year-old Ellenbrook man and a 16-year-old Alexander Heights boy who all face charges under the out-of-control party laws.
Follow WAtoday on Twitter @WAtoday
