THE brawl that erupted at the Mandurah Aquatic and Recreation Centre last night has been brewing for days.
Acting Superintendent Dean Snashall said there was an incident at Coodanup College on Thursday and another incident at Billy Dower Youth Centre.
In response to the incidents, those involved had been involved in mediation.
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READ NOWActing Supt Snashall said the tensions had been between children of two families initially, but adults became involved last night.
It was about 30 seconds into the end of an under 13 girls basketball game, when a fight started.
About 15 police cars attended and police found about 50 to 60 adults and children, with some fighting.
A 58-year-old referee was taken to Peel Health Campus, but was soon released.
A 35-year-old woman and a 17-year-old juvenile have been taken into custody.