The Wairarapa community are demanding answers to what caused children at Carterton South End's school to become sick, after a strange smell wafted over the school yesterday afternoon.
Police ruled out initial reports that a plane flying overhead may have dropped a toxic substance on the school.
Parents at the school are angered and want answers as to what caused the illnesses.
Cody Pratt's daughter was one of the students who vomited after smelling a sulphur like substance.
"It was scary having my daughter in the school premises and being told I couldn't go in to get her was pretty daunting," said Mr Pratt.
"I definitely want to know what has gone on.
"Children came in after lunch and reported feeling unwell after the substance, or smelling a smell," he said.
Ten students were taken to hospital but returned to their homes last night.
The school was cleared to be re-opened for classes on Monday.
Police say they have conducted a thorough examination of the school and still haven't found a point of cause.
Police inquiries will now focus on the surrounding neighbourhood.