A police investigation is underway at the Carterton school where 10 primary school children were taken to Wairarapa Hospital after falling ill yesterday afternoon.
Emergency services were called to South End School at approximately 1pm yesterday with reports of an unpleasant smell.
Paramedics treated 40 other people - children and adults - with minor symptoms and over 100 people had to go through a decontamination process.
Police searched the school grounds this morning but were unable to find the source of the smell, Wairarapa Area Commander Inspector Scott Miller said.
"Witnesses have described seeing a grey and white or red and white plane, possibly a Cessna, flying near the school between 1.30 and 2.30pm yesterday," Inspector Miller said.
While there is no evidence to indicate the plane is the source of the smell, though Inspector Miller says they'd like to speak to the pilot.
"The CAA is also trying to locate the aircraft."
Board Chair Brian Chin says children who left their belongings at the school last night will be able to collect them on Monday, when school "resumes as normal".
"A debrief with staff with happen next week."
Anyone living close to the school with any further information is urged to get in touch with Masterton Police on (06) 370 0300.