Two teenagers were charged with supplying drugs at under-18s music festival Lost City on Saturday night, while 14 others were found to have illegal substances.

A 14-year-old girl from Mt Druitt was allegedly found with 31 MDMA capsules. She was granted bail to appear at a children's court in April.

Crowds of teenagers at the Lost City music festival. Credit:Brook Mitchell

Police also charged a 17-year-old boy from Wangi Wangi, who was allegedly found with 75 MDMA capsules. He was also charged with resisting arrest and possessing a knife.

The crowd of roughly 12,000 13- to 17-year-olds were almost universally well-behaved, with just 27 ejections for intoxication, drug-related matters and anti-social behaviour.