Couillault has not yet been told about when the siblings were infectious, so he does not yet know whether they will have a large number of other students who will now be considered close contacts.
But he said both siblings "attended regularly" last week, indicating that they were probably at school until Friday.
Covid-19 modeller Professor Shaun Hendy said it would be important to know whether these were "downstream cases" that caught the virus from the known cases - or whether they were "upstream" - and the original source.
"If it is the latter then this could be the sign of a significant cluster. If it's the former there is still a good chance the cluster is contained."
Asked about the testing of close contacts, Hipkins said of the 31 close contacts in Papatoetoe High School, 29 have been tested 28 are negative, and one is positive.
The other one has not come back yet.
In terms of tests of staff at the LSG Sky Chefs - where one of last week's three community cases works - officials are still awaiting a few results.
Meanwhile, officials are looking at "every potential opportunity there could have been for infection", Hipkins said.
A "big wave of testing" is designed to find out if there are any more Covid-19 positive people in the community.
Hipkins is providing an overview at a select committee of what has been done so far to contain the latest community cases, as well as what the plan is for the coming weeks.
Hipkins decided to make the new community cases known at the committee meeting, rather than waiting until the 1pm statement, because in the past the news of any new community cases has leaked out.
Bloomfield is at the committee too.
National's Shane Reti, as expected, again asked Hipkins about saliva testing. He grilled the Covid Minister in the House yesterday.
These changes include: Air filtration systems in all facility lifts are being replaced, CCTV systems has been upgraded and people's movements have been further limited.
Over the last few days, National has said the Government has done the right thing by putting Auckland at alert level 3 and the rest of the country at level 2.
But they have been zoned in on the issue of saliva testing.
National's Reti says this method should be mandatory and done every day to people in MIQ.
But, speaking in the House yesterday, Hipkins said this method was already being used in tandem with the nasal swaps.
However, he said saliva testing was not as accurate as the current method and would not be used by itself as a means of testing.