NSW Police say 12 children were strip-searched at an under-18s music festival on Saturday, including six who were allegedly found to be concealing drugs "internally".

Key points: Of 44 teens searched at the Good Life, Lost City festival, 11 were strip searched

Police allegedly caught a 14-year-old girl and a 17-year-old boy with more than 100 ecstasy pills

A 15-year-old was instructed to expose his genitals during a search at the same festival last year

A total of 44 children were searched at the Good Life, Lost City festival — an event for teens aged 13 to 17 — at Sydney Olympic Park on Saturday.

NSW Police said 11 of the 12 strip searches conducted during Saturday's festival resulted in positive detections.

Six of the children subjected to strip searches allegedly possessed drugs that were "concealed internally".

This included a 16-year-old girl who allegedly internally concealed 4 grams of ice, and a 14-year-old girl who allegedly concealed 31 MDMA capsules.

Two 15-year-old boys allegedly internally concealed 11 and three MDMA capsules each.

Officers removed 27 people from the event. ( ABC News: Bruce MacKenzie )

"If a person retrieves an item concealed internally and provides that item to police, that event is classified as a strip search," a NSW Police spokesperson said.

But legal experts say that classification is incorrect.

"A person can removed an item from their own body cavity without under going a strip search," Redfern Legal Centre's Samantha Lee said.

It comes one year after police instructed a 15-year-old boy to expose his genitals as part of a strip search at the same festival.

After complaints from the public last year, the state's police watchdog investigated the use by police of powers to conduct strip searches on minors.

The Law Enforcement Conduct Commission (LECC) inquiry heard police conducting strip searches on children was potentially unlawful.

Ms Lee said if police were to strip-search a minor, they should ensure a parent or guardian was present.

"If they're not going to have a parent or guardian present, then they must have a very good reason as to why that person isn't going to be available," she said.

NSW Police said all strip searches conducted were lawful.

However, legal experts have questioned whether children could be properly informed about their rights.

"In this circumstance, the festival did not allow a parent or guardian in to accompany the child, so it is unclear what information was provided to the child that ensured that fully understood the testing they were being subjected to," Ms Lee said.

At least 30 children were strip-searched at the same festival in 2019, but it is still not known how many were caught with drugs.

"What we know is that in the majority of strip searches absolutely nothing is found, and what we do know for sure is that strip searches are traumatic, invasive and … therefore should only occur as an absolute last resort," Ms Lee said.

Police said a total of 14 teenagers were caught with prohibited drugs at the festival.

Officers also removed 27 people from the event for intoxication, drug-related matters and anti-social behaviour.

The NSW Government has been contacted for comment.