Four children were taken for a hospital check-up after coming into contact with “tablets” at a West Yorkshire primary school.
The alarm was raised around 1pm today at Holywell Green Primary School near Elland.
A woman in her 20s has been arrested in connection with the incident.
West Yorkshire Police has not said what was in the tablets.
One parent claimed a bag of drugs was brought into the school on Stainland Road by a child.
In a statement the force said: “Police were called at around 1pm to an incident at a primary school in Elland in which some children had come into contact with what believed to be tablets.
“Four children were taken to hospital as a precaution, but have since all been discharged.
“A woman in her 20s has been arrested in connection with the incident.
“Enquiries are ongoing to establish the circumstances.”
Calderdale Council’s Director for Adults and Children’s Services, Stuart Smith said: “We are aware that some children from a school in Calderdale have attended hospital today and their parents have been informed.
“Police and social workers are investigating the circumstances.”