Police are investigating a complaint about a serious sexual incident in Picton on Tuesday night or early yesterday morning.
Detective Constable Lindsay Tilbury said police had interviewed a male suspect, but no charges had been laid yet.
The investigation into the complaint was continuing, he said.
"This is very serious, and we are not taking it lightly. We want to complete the investigation before laying charges."
It is understood the incident may have happened near Picton Primary School, in Buller St. Police were seen at the school early yesterday morning.
Mr Tilbury encouraged anyone with any information about the incident to contact Blenheim police on 03 578 5279 or phone Crimestoppers on 0800 555 111.
"We'd be keen to hear from anyone," he said.
No further details on the incident were available last night.
Police were also not available yesterday to give details on any incidents reported or people arrested during the holiday period, including New Year's Eve, although police regional commander Inspector Simon Feltham said yesterday they had been happy with crowd behaviour at Blenheim and Picton.
- The Marlborough Express