About 160 people were searched by police drug dogs at the Knockout dance party for the Midnight Mafia festival at on Saturday evening.

Nineteen were found to be carrying drugs, mostly the amphetamine MDMA that lifts excitement and can create feelings of euphoria.

Three men were arrested and charged with supplying prohibited drugs including a 22-year-old Jesmond man found with 35 tablets, a 23-year-old Peakhurst man carrying 124 tablets, and a 22-year-old Marrickville man found with 441 tablets.

A 25-year-old Allambie Heights man is alleged to have had more than $2500 cash on him and has also been charged with supplying drugs.

An additional 16 people were charged with possession of MDMA tablets.

South West Metropolitan Region Detective Inspector Gus Viera said while the crowd was generally well-behaved there was an ongoing issue with a lack of quality control of illicit drugs so police would continue to attend similar dance events.

"Quite simply, you don't know what you are getting. Seeking a synthetic high could result in a serious injury or death," Detective Inspector Viera said.

New South Wales police  would  continue to arrest people who supplied and used illicit drugs at dance parties, he said. "Everyone has the right to attend these events and remain safe in a secure environment."

Four people were taken to Concord Hospital after experiencing adverse effects of drugs. All are expected to make a full recovery.

The significant arrests come a few days after 19-year-old Rebecca Hannibal pleaded guilty to supplying her friend Georgina Bartter with an ecstasy pill that led to Ms Bartter's death.  Ms Hannibal will be sentenced in June.

Matthew Forti, 19, who sold Ms Hannibal the pills, pleaded not guilty to supplying the ecstasy pills when he appeared at the Downing Centre Local Court in March. His solicitor has requested a MERIT order that would refer him to a drug-treatment program.

Fairfax Media