Story now up on RNZ:
A student at St Dominic's Catholic College in Auckland has tested positive for Covid-19, and has been linked to the sub-cluster.
The student was last at school on Friday but left early after starting to feel unwell.
Hipkins said in this case it appears that it was a close contact of the sub-cluster that had not been previously disclosed.
The authorities are now looking into whether that was on purpose.
"That's one of the things that the investigation is looking at now and it will include looking at whether there was a deliberate decision not to disclose, or whether it was simply an oversight," Hipkins said.
He said this sub-cluster has been a challenge to work with as some members do not understand the seriousness of the situation.
Bolding mine. I don't know how infectious you can be before you're symptomatic enough to want to leave school sick, but this is a concerning development.