Five school pupils became unwell today after eating sweets shared by another student.
Police are investigating the incident at The Wensleydale School in Leyburn.
Police were in school today and have taken the sweets away for analysis.
The children were taken home by their parents and are understood to be feeling better this evening.
It is understood the sweets were a well-known brand of jelly sweets.
Headteacher Julia Polley has issued a statement to parents this evening about the incident.
She said: “This morning five students became unwell after eating ‘sweets’ shared by another student.
“They have all been given the appropriate medical attention and their parents have been informed.
“We are taking the matter very seriously and the bag of sweets in question has been confiscated and we are investigating how such a thing could have happened.
“We are working very closely with the police, who have taken away the sweets for analysis.
“I would like to take this opportunity to reassure all parents and carers that we take safeguarding extremely seriously and our students’ safety is our utmost priority.”
Mrs Polley urged parents and carers from discussing the incident on social media “as rumour and speculation can cause unnecessary upset and panic”.
A North Yorkshire Police spokesman said: “Police are working closely with the school as part the ongoing investigation into this matter.
“If anyone has information that could assist our enquiries, please contact North Yorkshire Police on 101, select option 1, and speak to the Force Control Room. Quote reference number 12210240267 when providing details.”
Earlier this year, police issued a warning about drug dealers lacing sweets with drugs such as THC, the active component of cannabis.