All works at a development at Shelly Bay in Wellington have been halted after kororā re-entered the site through tampered fencing.
The fencing, which blocks the penguin from getting into the site, is thought to have been raised by a member of the public.
Over the weekend members of the public posted concern on social media after coming across penguin on Shelly Bay Rd at night.
The posts were picked up by the developers and a penguin specialist and penguin detection dog were on-site on Sunday.
Surveying confirmed more than one kororā had got back into the site, where they have been known to nest.
Wellington iwi Taranaki Whānui are working with The Wellington Company for the development and leading the kororā management with experts.
Their worksite kaitiaki, Charlie Rudd, said it was disappointing the penguins had been able to get back into the site.
"It sounds like people have acted with hearts, but not with heads and allowed the kororā in - and it's dangerous"
Rudd said the penguin-proof fencing had been up since before the demolition of some buildings took place, which was a couple months ago.
He confirmed that until this weekend, the site had been free of kororā.
"Now we're assuming there is more kororā, so we need to completely clear the site, understand where they are and then we've got to accommodate them - this is not about any development this is about the kororā now" Rudd said.
One option could be to isolate the part of the site which the kororā had returned to.
"That's fluid, that's always changing so we've got a plan, but not all plans are robust so we've got to move with the kororā - so what's important for us is to accommodate how they move."
Rudd said he worked closely and on an ongoing basis with Dr Leigh Bull, an ecologist and penguin expert of Boffa Miskell Ecology.
There are a number of groups involved in part with managing kororā on the site - Boffa Miskell, The Department of Conservation (DOC), Places for Penguins Wellington, and The Wellington Zoo.
"The goal is to keep [kororā] out to danger and try mitigate that as much as possible," he said.
There were previously nests at northernmost part of the development prior to the demolition of a building on site - around where the kororā were sighted on the weekend.
Along the fenced off area there is a gap to four temporary nesting boxes, which is directly across from a large seawall on the beach which penguins cannot scale.
But Rudd said the kororā were known to cross the roads and would continue to wander across regardless.
They had to walk up to 100m to get to the boxes, but Rudd said kororā were tenacious.
"They will poke across the whole perimeter of the fencing and then they will find the gap [to the boxes] and it's a temporary fix for them.
"Then they might say, 'hey, we don't like this - we're going to go out and find another home'," Rudd said, noting that areas further away from the site were rocky and more suitable for nesting.
DOC operations manager for Kapiti-Wellington, Angus Hulme-Moir, said there would be a clearer plan in the coming weeks.
"A draft plan has been written by Boffa Miskell ecologists, with a finalised penguin management plan expected in three to four weeks. Penguins are being managed across the site in the interim, and the developer is supportive of this work."