Police have arrested a youth in connection with a threat to shoot a teacher and a number of pupils in Leiden.

No further details have been released but police confirmed the youth is a former pupil at the British School in Voorschoten. He was expelled in October 2011 for bad behaviour and has not been seen at the school since, the Telegraaf reported.

It is not clear why the youth’s former school is being considered relevant to the investigation. According to RTL news, the youth is being questioned by police on Monday afternoon.

The British School’s secondary department, for pupils aged 11 to 18, is located in Voorschoten. The school was open as usual on Monday but there was extra security.

Leiden

All secondary schools in Leiden were closed on Monday after police were tipped off about an internet threat. The anonymous threat was made against an unnamed teacher and ‘as many pupils as possible’, Leiden mayor Henri Lenferink told Nos news.

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’.

Delft University computer science lecturer Johan Pouwelse told RTL news threats made on 4chan should always be taken seriously because of the type of users it has. ‘The rules [for the site] are on paper only. In practice the users can come and go as they please,’ he said.