A total of 16 people were hospitalised for suspected drug-taking at three music festivals across regional Victoria and Sydney over the weekend.

Six people at the Rainbow Serpent music festival in Victoria's west were taken to hospital after suspected drug overdoses at the event, which was in its fourth day.

Ambulance Victoria said it took a man in his 20s to hospital in Ballarat mid-morning on Sunday after a suspected overdose at the site.

On Saturday, paramedics transported a woman in her 20s in a stable condition just before 7:30am, while three men were hospitalised on Saturday afternoon and evening in a similar condition.

On Friday morning, a man in his 20s was taken to hospital in a critical condition.

Police also made a series of arrests at the event.

Since Friday, four men and a woman were arrested for drug-related offences, including the trafficking and possession of ketamine and MDMA, as well as assault.

Seventeen other people caught in possession of drugs were cautioned.

More suspected drug-related incidents at Sydney festivals

Meanwhile in Sydney, 14 people were taken to hospital and 57 were charged with drug offences after two music festivals on Australia Day.

Six men in their early 20s were sent to hospital in a critical condition from the Hardcore Till I Die festival at Olympic Park.

Eight others were taken to hospital from the Electric Gardens festival in Centennial Park in Sydney's east.

Seven people were in a stable condition and the remaining seven have been discharged from hospital.

Dr Mary-Anne Gale from NSW Health said 10 of the admissions were likely to be drug-related.

New South Wales Health said it was on high alert ahead of the Rolling Loud Festival at Sydney Olympic Park on Sunday.

Suspected overdoses follow on from 'horror' start to weekend

The developments came in the wake of what police described as a tragic start to the Rainbow Serpent event late last week.

A 19-year-old Yarraville woman died on her way to the festival after the car she was travelling in crashed at Gordon on the Western Highway on Thursday.

Police said they were disheartened by the tragedy that occurred at the start of the Rainbow Serpent festival. ( Flickr: Eliza Tyrrell )

Just hours later, an unoccupied truck rolled onto a tent at the festival site, seriously injuring three people inside.

Two women and a man were still recovering in hospital as a result of the truck rollover. Police at the time said the vehicle belonged to the festival's management.

The event organisers said they would comment on the incident after the festival ended on Tuesday.