More than 100 people have been charged during the first day of the two-day Stereosonic music festival, police say.

More than 50,000 people attended the festival at Sydney Showground, on Saturday.

More than 200 police officers were on hand.

On Saturday officers searched 565 people and charged 119 people, 105 of them with drug-related offences.

Thirteen people were charged after allegedly bringing alcohol into the venue and four were arrested over alleged assaults.

Police say they seized illegal drugs including cannabis and ecstasy tablets as well as alcohol.

Superintendent David Eardley, says police will continue to target anti-social behaviour and any alcohol or drug-related crime on Sunday.

“While a number of people chose to do the wrong thing, it’s pleasing to see that the vast majority of revellers enjoyed the beginning of the festival safely,” he said.