Four children have been taken to hospital from South End School in Carterton

The school says about 1pm a strong smell was detected in the playground and several students have since reported feeling dizzy and unwell.

In a Facebook post, the school is saying a student saw a plane dropping a substance they believe to be fertiliser near the school.

Carterton senior fire officer Wayne Robinson says 20 children are showing signs of illness, including vomiting, and four have been taken to hospital.

All staff and students are to be showered and parents have been asked to bring a change of clothes for their children.

No students are currently allowed to leave the school grounds, and no one is permitted on to the grounds.