Police have arrested a former pupil after an online message threatening a shooting closed 22 schools in the Netherlands.
The schools in the western city of Leiden were warned to stay closed today, after the message on the 4chan internet forum.
The student's identity is unclear, though police have confirmed he is male, and The British School of the Netherlands has confirmed that one of its former students has been arrested in connection with the threats.
In the message, in English, the author threatened to "shoot my Dutch teacher and as many students as I can," adding: "It's at a school in the Dutch city of Leiden. For more proof, I will be using a 9mm Colt Defender.
"Oh, and I'm using a proxy, the police is not gonna find me before tomorrow."
In a statement, police said: "Police have received mention about a possible school shooting (being planned) in Leiden.
"In light of this serious threat, it has been decided not to take any risk and therefore all middle schools will remain closed on Monday."
Hague police spokeswoman Yvette Verboon confirmed the arrest, and said police are "investigating his involvement" in the threat that was discovered yesterday.
According to Dutch media, two of the main schools, Da Vinci College and Driestar College, had police officers outside them this morning.
Frans van der Mark told the BBC he received a phone call from his children's school late on Sunday night advising he keep them at home.
"I was completely surprised and I have to admit I was trembling when I received the call. I couldn't sleep as a result," he said.
Leiden Mayor Henri Lenferink told state broadcaster NOS: "It could just be a morbid joke but we don't want to take any risk."
But Ton Duif, chairman of the head teacher's association, AVS, said: "Every idiot who sticks a threat on the internet can paralyse half of society."
Shooting rampages are rare in the Netherlands, where gun ownership is tightly controlled.
The city, home to the country's oldest university, is just northeast of The Hague.