40 people have been charged with drug offences in a police operation during the first two days of Subsonic Music Festival.
Police attended the grounds of the electronic music festival at Riverwood Downs, Monkerai with sniffer dogs from Friday to Sunday.
On Friday, police arrested and charged 17 people who were allegedly found in possession of illicit drugs, and three others who were charged with supplying a prohibited drug.
Police said they were "disappointed" the festival attendees continued to ignore drug warnings on the event's second day, where a further 20 arrests were made.
The people arrested were allegedly found in possession of various illicit drugs, including amphetamines, LSD, Ketamine, cannabis and ecstasy.
Superintendent Chris Craner, Commander of Port Stephens Local Area Command, said it was disappointing festival goers were still breaking the law and continuing to put lives at risk by supplying and consuming illicit drugs.
"Police are disappointed and shocked with the number of people carrying drugs and personally putting their own health and the health of others at risk," Superintendent Craner said.
"Consuming a prohibited drug is extremely dangerous – you don't know what is in the drug, how and where it has been manufactured, or what effects it can have on your body.
"The illegal activities at these events will put the future of any such event in this area in serious jeopardy," he said.
The operation was due to continue on Sunday, when the festival was due to finish at 10pm; however, police are so far unable to confirm whether any further arrests were made.
Most of those charged will face Dungog Local Court on 11 January 2016.
The arrests follow the controversial announcement by harm minimisation activists that privately-funded pill-testing kits would be made available at Sydney's summer music festivals, a movement opposed by the NSW government.
Fairfax Media has partnered with the Global Drug Survey for its fifth year to help understand how and why people take drugs in Australia.
