Several pupils have been taken to hospital after collapsing at a secondary school.
Around 27 students displayed signs of sickness and feeling faint at Outwood Academy School in Ripon, North Yorkshire Police said.
It is not yet known what caused the students to fall ill and emergency services remain at the scene.
The incident is believed to have happened between 11am and 11.30am.
A police spokeswoman said: "Approximately 27 students have been affected who have displayed signs of sickness and feeling faint. Some have been attended to by paramedics at the scene and others have been taken to hospital.
"At this stage it is not known what has caused the students to fall ill and officers are working with the fire service to establish what has caused the incident."