Hastings District Council has managed Frimley Pools for the past year and a half.
A council spokeswoman said a chlorine test was carried out by pool staff by 10.40am and came back as being in the average range.
The regular 8am test had also been within the same range. Further water testing has been referred to a commercial water testing agency, and initial results from those tests were expected tomorrow with comprehensive results expected by Saturday.
When asked what he thought caused the outbreak, Mr Hensman said every theory seemed to be cancelled out by new evidence.
Only about 350 of the school's students had been at the pools. After they returned to school ill students were picked up, and there had been no new reports of students feeling ill.
"No one at school seemed to be affected, whatever it was it was contained fairly quickly.
"The cause is a mystery."
By mid-afternoon, Mr Hensman said: "We're confident the students who were affected are better, and that's the most important thing."
A father who picked his "shaky" 13-year-old daughter up from Taradale High School yesterday said parents had been told to seek medical advice for their children.
He thought the sickness must be "patient to patient", as by mid-afternoon his daughter was feeling better but some of her friends were not.
"It's a bit worrisome when they're saying the chlorine levels are fine.
"If the chlorine levels are fine there must be something else in there [the pools].
"I want them to find out what's wrong, that's for sure."
Part of today's Sanitarium Weet-Bix Kids Hastings TRYathlon was due to be held at Frimley Pools. The course would now be a run-bike-run.
Sanitarium spokesman Peter Levett said the health and safety of its participants was the company's primary concern, and for this reason the decision had been made to cancel the event's swim leg.
Hastings District Council's pools manager Alice Heather said it was expected the pools would be able to be reopened on Saturday.
