Police would like to speak to the occupants of a white van which was seen in the area at the time of the assault.
"We'd also like to hear from anyone who saw people dressed as clowns in the city overnight between 7 - 8 October."
Anyone with information was asked to contact Hamilton Police on (07) 858 6200 or Crimestoppers on 0800 555 111.
The incident follows a sighting of a man dressed as a clown who frightened children near a Porirua school on Wednesday night.
Three boys were playing basketball at Discovery School in Whitby when they saw the man in clown makeup or a mask behind a building.
Police didn't find anyone matching the description when they arrived.
These incidents come as a "creepy clown epidemic" reportedly sweeps the United States, with numerous reports of clowns trying to lure children into the woods prompting extra security at some schools.
Many sightings of scary clowns and reports of them frightening people have turned out to be pranks, and police have complained that is leading to a waste of their resources.
The hysteria which followed the sightings resulted in a "Clown LIves Matter" march, organised by professional clowns who said they were being unfairly maligned.
A remake of the clown horror film It, adapted from the Stephen King novel of the same name, is due to be released next year.
