Two children have allegedly been assaulted at the St Peter Port bus terminus.
Police say it happened at around 5:25pm on Tuesday 31 May.
Officers want to speak to anyone who saw what happened.
The force also wants people in the South Esplanade and bus terminus area with CCTV to come forward.
Anyone with information is asked to call PC55 Le Bachelet on 222 222 or Crimestoppers anonymously on 0800 555 111.

Guernsey charity GROW asks for help in tracing missing stock
Jersey drone havoc: Specialist equipment on-island
Guernsey ambulance fees to rise
Guernsey vet struggles during long wait for work permits
Guernsey charity appeals after £700 worth of goods go missing
Search in Jersey for drone pilots who disrupted airport flying
Guernsey Museums report a 3% increase in visitor numbers
Sewage outfall fixed on Guernsey's east coast