Debbie Tesoriero's 16-year-old son Jack spent the night in hospital after he was punched and had his phone stolen at the event, she said. "My understanding is that he was knocked out. He didn't know where he was, he didn't know what day it was," she told the Seven Network. It's believed he had been walking a friend back to a car when he was jumped by the group, she said. One witness, Joe Cuic, said a "big pack" ran through the crowd, grabbing mobile phones and handbags as festival-goers recorded the fireworks. He then saw youths throwing rocks at apartment buildings.

"Out of nowhere, everyone's gone from standing there watching, having a lovely time, to people just running in all directions," he told the Seven Network. Abhishek Verma was dragged into a scuffle when he chased after two teenagers who had just stolen his wife's phone. "All of a sudden like 30 or 40 came and they started punching, kicking," he told the Seven Network. No one has been arrested.

The alcohol-free, family event is run by Melton City Council and features music, rides, a food hall and market stalls. Melton Councillor Steve Abboushi, who attended the event with his family, said it was disappointing to see the festival end in such a way. "It was a perfect event, even better than we anticipated, but you can't control when, at the last minute, people decide to come in and gatecrash your event," he said. "I'm really shocked and concerned at these reports." He said the incident is another example of why Caroline Springs needs more police in the area.

Melton Council acting CEO Maurie Heaney said there were "tens of thousands" of people at the event. "Security and police were present on site for the duration and until large crowd numbers vacated the event," he said in a statement. "While council has become aware of reports of theft and assault through the media, to verify any offences or investigations, council directs all inquiries to Victoria Police." Witnesses described the offenders as being mostly teenage boys of African appearance. Females and Caucasian teens were also in the group. A witness, Penny, told the Nine Network it was a "great big mass of people" moving through the crowd.

"It was like a stampede, it was awful," she said. Another witness, Carrie, told News Corp she also had her phone and wallet stolen and was shoved in the stomach. "It was a planned attack," she said. Anyone with information about the incident is asked to contact Crime Stoppers on 1800 333 000 or www.crimestoppersvic.com.au. With AAP