Detective Sergeant Andrew Mortimore of the Hamilton CIB believed other similar incidents within the greater Hamilton City area may have gone unreported.
"We'd like to hear from anyone who has had a similar experience," he said. "We believe they may have important information that can assist this investigation."
Information can be provided directly to Hamilton Police by calling 07 858 6200 or anonymously via Crimestoppers on 0800 555 111.