All secondary schools and mbo colleges in Leiden will remain closed on Monday on police advice because of a threatened shooting.

The anonymous threat was made on an internet site against an un-named teacher and ‘as many other pupils as possible’, Leiden mayor Henri Lenferink told Nos news.

Police have been investigating the threat but have so far failed to find out which school is at risk, leading to all secondary schools being shut down.

Police guards

In addition, police officers will step up their surveillance of secondary schools and mbo colleges in the city, Lenferink said. Police and council officials are taking the threat ‘extremely seriously’, website nu.nl reported.

Nos states the threat was placed in English on the international website 4chan.org at the weekend and stated ‘tomorrow, I will shoot my Dutch teacher, and as many students as I can’. The author also said he or she would have a note with them when they entered the school, explaining why they were doing this.

In 2009, police in Rijsbergen arrested an 18-year-old boy who used the same website to threaten to start shooting at a school in Breda which turned out to be a hoax, nu.nl reported.