Police in Spain are investigating about 50 reported cases of women getting pricked with medical needles while at nightclubs or parties, a trend that previously came to the attention of authorities in other European countries.
So far, Spanish police have not confirmed any cases of sexual assault or robbery related to the jabs.
Waves of needle attacks at musical events have also confounded authorities in France, Britain, Belgium and the Netherlands.
French police have tallied more than 400 reports in recent months, and said the motive of the jabs was unclear.
In many cases, it also was not clear if the victims were injected with a substance.
Spanish police have so far found evidence of drugs in one victim, a 13-year-old girl in the northern city of Gijon who had the party drug ecstasy in her system.
Local media reported that the girl was quickly taken to hospital by her parents, who were near her when she felt a prick with something sharp.
In an interview with national public broadcaster TVE that aired on Wednesday, Spanish justice minister Pilar Llop urged everyone who thinks they received a jab without their consent to go to the police, since being stabbed with a needle “is a serious act of violence against women”.
Spanish health authorities said they were updating their protocols to improve the ability to detect any substances that were possibly injected into victims.
The toxicological screening protocols call for blood or urine tests within 12 hours of a suspected attack, Ms Llop said.
The guidelines advise victims to immediately call emergency services and go to a health center as soon as possible.
In south-west France, a spate of needle attacks were reported during the Bayonne Festival, which about 1.2 million people attended last week in the city near Spain’s border.
Bayonne deputy prosecutor Caroline Parizel said 124 people received medical examinations after they reported potential needle attacks.
They included both women and men.
Eleven filed legal complaints.