Key Points:

A 15-year-old Rotorua boy has been charged with sexually violating a 13-year-old girl in a park.

The girl called police about 2am on Saturday, Detective Lehi Hohaia, of the Rotorua police, said.

She was found with friends in the Corlett St Reserve that runs between Corlett and Konene Sts.

Soon after Rotorua police arrested a 15-year- old youth.

He will appear in the Rotorua Youth Court today charged with sexual violation by unlawful sexual connection.

Mr Hohaia said the investigation was still in its early days.

"We have to get a specialist interviewer in to talk to the girl and we have about 12 youths to speak to as well.

"There is a lot of information to sort through so the investigation will take some time," he said.

Mr Hohaia said police were unsure as to why the girl was in the park at that time of night.

"We believe her parents didn't know she was out at the time."

The girl had not been drinking and did not know the boy, who was believed to have consumed alcohol, he said.