A wild brawl involving about 50 teenagers broke out in Melbourne's southeast overnight with riot police forced to use pepper spray on the group.

On Wednesday night about 9.30pm, police received reports that about 40 to 50 youths were pushing and yelling in the streets near Chelsea train station.

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They had been moved from the beach by officers and agreed to get on a bus with the intention of leaving.

But as they boarded the bus, a fight broke out between two groups involving about 30 people.

Police were called to Chelsea train station on Wednesday night. Credit: 7NEWS

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Police used pepper spray to stop the fighting and a majority of the teenagers were taken to Chelsea police station.

An 18-year-old male was arrested, but released while police make further inquiries.

Police used pepper spray to stop the fighting. Credit: 7NEWS

No one was injured during the incident and police remained in the area throughout the warm night to ensure community safety.

This came after Melbourne copped a scorching 39.7C day on Wednesday, with thousands losing power across the state.