Police in Häme, south-central Finland, are investigating reports of a threat against a school received last week.
In a statement on Wednesday, police said that three female minors were taken into custody last Thursday after searches of their homes. They are suspected of planning an attack on a school in Riihimäki, a town of 30,000 people some 70 kilometres north of Helsinki. No weapons or explosives were found in their possession.
Two of the girls remain in police detention, while the third is in the custody of other officials. Police have informed the school administration, which has discussed the matter with the pupils' parents.
"We heard about this on Tuesday evening when a student's guardian informed school officials that a WhatsApp message in circulation that included threats against three schools in Riihimäki," says the town's education director, Esa Santakallio.
Police had apparently been aware of the matter for several days by then.
"I think the police have handled this in an excellent manner," says Santakallio.
"Schools remain safe"
Santakallio told Yle on Wednesday that he was still not sure how serious the threat was, but that Riihimäki's schools remain safe.
"All our schools have security plans in case of various types of threats. These plans include clear instructions, which are practiced and followed in all threatening situations," he says.
"The schools have not heard of anything beyond these messages. The police are responsible for providing information, and will make further statements if need be."
On Wednesday, Riihimäki schools sent out a message about the incident to parents, guardians and pupils via the Helmi electronic data system.
Concerns taken seriously
Santakallio says that schools take students' worries seriously, and urges them to speak to a staff member about any such concerns.
He says that the appearance of such threatening messages is an indication "that young people are in distress and on the other hand that these kinds of fads appear...they are always taken seriously," he adds.
Riihimäki, home to the Sako gun factory since 1927, is some 30 kilometres from Jokela. A November 2007 school shooting there left nine people dead.
In mid-November, a young woman went on trial on suspicion of planning a school attack in Kokkola, western Finland, apparently partly inspired by the Jokela tragedy.