The incident happened sometime between 20:00 on Wednesday 11 November and 10:00 on Thursday 12 November along Contree Mansell in St Peter Port.
Anyone that was in the area at the time and thinks they might be able to identify those responsible is asked to contact PC 135 Simmonds on 725111.
People with information can alternatively contact Crimestoppers anonymously on 0800 555 111.