Hipkins said the St Dominic's student was linked to a close contact of the church sub-cluster that had not previously been disclosed, and authorities were investigating whether the non-disclosure 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.
Swann told Māori Television today that she did not blame the student or her family.
"It's not their fault. It's no one's fault when someone gets sick," she said.
"I know that people react often to situations like this out of a bit of fear, but this is not something to be fearful of.
"This young woman is undergoing a lot of pressure and a lot of emotion for someone so young, and her family are under incredible pressure. This is nobody's fault.
"We are supposed to be here for each other, to take care of each other, regardless of whatever happens, and it's really important that that message gets out there."
The college has been closed until Monday for a "deep clean" after the student tested positive for Covid-19 on Tuesday.
Swann told parents that "all activities planned for the rest of this week have been put on hold until further notice, this includes senior prelim exams".
The decile-5 Catholic girls' school has an ethnically mixed roll of 838 girls - 29 per cent European, 28 per cent Asian, 24 per cent Pasifika, 11 per cent Māori, 6 per cent from other ethnicities and 3 per cent international students.
Swann said her priority was to make sure that the affected student and her family "feel completely supported by us".
"We are a whānau and we need to be there for her and her whānau," she said.
Asked about Hipkins's comment that some members of the Mt Roskill fellowship "do not understand the seriousness of the situation", Swann said the college took the situation very seriously.
"We take this very seriously because this is a health issue and this is our school and we care very deeply for it, and that's why we are following the Ministry of Health so closely," she said.
"They have been amazing, actually. They have been clear and constant in their communication right up to the late hours of last night - making sure that I felt supported, that our community is getting the information that they need."
She said she had spoken to the affected student and her whānau.
"I think they feel supported at the moment," she said.
"I know there is a process they have to go through to try and make sure that everybody can be accounted for and all of that factual stuff that needs to come out.
"I'm praying that they are being looked after. They are going through their own emotions and their own whānau time together as they work through this."
Swann said she had also been in touch with other West Auckland schools, who were all "very supportive".
"We are a very close bunch out west and we look after our own, and that's been really highlighted for me over the last few hours," she said.
"We are not siloed in this. We are one whānau and we need to look after each other."