Santa Margalida police suspect that a "drunk" or a "yob" wanted to cause panic when he used a needle on a 13-year-old girl at a Can Picafort fiestas party.
Tests carried out on the girl have so far proved negative, although some further results from "optional tests" have yet to be received. The police believe that the man, who the girl said was aged between 20 and 30, had wished to exploit current anxieties about needle spiking.
A report into the incident is being forwarded to a court. The police and the Guardia Civil are meanwhile trying to trace the man.