The alleged assault occurred on the evening of January 16 last, when it is alleged the teenage girl was lured to meet a 16-year-old boy near a Lidl supermarket in the town and then accompanied to a nearby wooded area.
It is understood the incident was reported to gardaí five days later.
It emerged yesterday that gardaí are reviewing the Facebook and BlackBerry Messenger accounts of a number of students in connection with the investigation.
Last week, The Mayo News reported that one line of inquiry being explored was the possibility the girl was being coerced into meeting the teenage boy through social media.
It is also understood images of the girl may have circulated on social media and via text messages before the alleged sex assault.
Nobody has been arrested and the Garda investigation is continuing.
A Garda forensic examination of the scene of the alleged assault has taken place, and the girl has attended the Garda Sexual Crimes Unit in Galway.
As many as a dozen schoolchildren may have to be interviewed by gardaí as part of the investigation, which will also entail reviewing recent activity on some social media accounts.
Gardaí could not confirm reports that Facebook and Blackberry Messenger accounts had been frozen as part of the probe.
The Government-appointed Special Rapporteur on Child Protection, Dr Geoffrey Shannon, has made a number of calls in recent years for new laws to deal with cases of cyberbullying, as well as a “whole school” approach to the problem.