Victoria police spokes-woman Senior Constable Melissa Seach said the man, 35, entered a tent on Jack Smiths Lane, Lexton, at 9.30am and indecently assaulted the woman.

A South Melbourne man was assisting police with their inquiries and was yet to be charged, Senior Constable Seach said. 

The popular four-day festival has been marred by controversy over recent years, with a man dying from a drug overdose in 2012 and five others admitted to hospital following excessive drug consumption in 2010.

The mother of 34-year-old Daniel Buccianti, who died in 2012, recently urged revellers to be safe ahead of this year’s festival.

Ambulance Victoria spokesman John Mullen said three festival-goers were transported to Ballarat Base Hospital on Saturday for suspected overdoses. One man, in his 20s, was unconscious and in a serious condition when he was taken to hospital at 4.20am, Mr Mullen said.

The festival, which attracts more than 10,000 people from Victoria and interstate, concludes on Monday.