On February 26, up to 600 youths congregated in the Woolworths car park in Ferntree Gully after the fireworks display on the first night of the festival.

Senior Sergeant Phil Edmunds, of Knox police, slammed the behaviour of the youths, saying there had been incidents of underage drinking, people playing "chicken" on Burwood Highway and "skirmishes" breaking out.

Senior Sergeant Edmunds said police had been forced to use capsicum spray to control the crowd. He said the youths had been in the car park waiting for public transport or to be picked up by their parents.

"It [the car park] is just not designed to do that. It's for the Woolworths [shoppers], not for people to congregate in and cause a nuisance.

"I'm just terribly disappointed with the youth in our area. But you can't put full blame on them. Parents have got to take a bigger responsibility."

Senior Sergeant Edmunds said many of the youths were between 12 and 16 and had been "out on the prowl".

He said some had been "very abusive" and may have been under the influence of alcohol.

Police issued five penalty notices for possession of alcohol. Two women and one man were arrested for breaching the peace.

It has also been alleged that youths waited outside two liquor outlets in Upper Ferntree Gully asking adults to buy alcohol for them.

Knox councillor and festival chairman John Mortimore said the incidents after the fireworks hadn't marred the festival as a whole, saying it had still been a fantastic family event.

"It just put an unfortunate accent on the evening's events.

"A very small minority of kids got involved in it, which is really unfortunate.

"The police did a great job."

Although the festival already has designated pick-up zones, police will meet Knox Council on the best way to handle crowds leaving the festival.