The police commander for Breckland said a disturbance involving up to 30 people in Dereham was an 'isolated incident'.
It happened in the Market Place at 8pm on Monday.
Chief Inspector Paul Wheatley said: 'It involved a group of youths and was an isolated incident, and not believed to be drug-related. There were no major injuries.
'We do regular patrols around Dereham town centre, and the investigation will continue.'
One man, aged in his late teens and from the Norwich area, was arrested on suspicion of affray and drug offences.
He was later released on police bail pending further enquiries until Wednesday, February 22.
Anyone who may have witnessed the incident should contact PC Matthew Hill at Dereham Police Station on 101.
Alternatively contact Crimestoppers anonymously on 0800 555111.
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