The ground floor was flooded, but the building itself was structurally sound, he said.
Cunliffe said many of the 300 houses which had flooded were in New Lynn and Kelston and included Parker Ave, Great North Rd, Atkinson Rd and Daffodil St.
"It's a human tragedy. You can imagine the flats that are the lowest-lying and most vulnerable are the cheapest and, therefore, they often have some of the most vulnerable people in them so there is a lot of tragedy for people who might be new migrants, uninsured, who aren't that robust anyway.
"So there is a lot of suffering going on in our community tonight."
In central New Lynn, a further 10 people were rescued from the block of shops on Great North Road opposite Clark St after the stream across the road overflowed and water rushed over the street.
"It was like a mini-Niagara Falls. It was completely unprecedented obviously."
"The block itself is now very precarious. It's been totally undermined by the river which has run across the road. [The building] is literally hanging off its foundations, very dramatic," Cunliffe said.
In the New Lynn shopping precinct a commercial building housing about six businesses was being treated as dangerous after severe flooding pushed the footpath into it.
The Fire Service evacuated the tenants from the building opposite Clark St which was severely flooded after a nearby stream overflowed and water gushed across the road. The flooding ran from Bike Barn to Harcourts on Great North Road and businesses in the worst hit building included Happy Japanese, Bula Barber and Le Fiafia Night Club.
Whau local board chairwoman and New Lynn Business Association contract manager Tracy Mulholland said it was a shocking sight and upsetting for the tenants.
She had spoken to one tenant who was visibly upset about leaving his possessions behind in the downstairs studio he was renting.
"I saw what looked to me to be a lake on the corner of Clark [St] and Great North [Rd] and I've been working in that area with shopping centres, local council and the transit project for 24 years nearly and I've never seen anything like it.
"It was literally flooded and I've never seen what looked like a footpath dropping into a building so what I saw was, for me, quite shocking in a metropolitan centre."
Mulholland had been in the town centre this afternoon and said everyone had been safely evacuated, but police, the fire service and council engineers were on site.
She had been told the engineers were waiting for the water to recede more so they could enter the building and assess the damage.
However, she said there were great concerns about its safety.
"What I do know is there is quite severe damage from what I have seen and heard because they are not always to tell you things straight away. It looked to me like the whole footpath and given way into the bottom of the building.
"That's the one building they are looking at because they fear there is risk although no one confirmed anything ... I would say there is absolute damage to that building."
A representative for Auckland Civil Defence and Emergency Management was unable to provide details at specific properties and said a number of assessments were being undertaken in the west Auckland area.
Labour MP David Cunliffe tweeted that New Lynn businesses faced a massive cleanup after the flooding.
He said the floods had caused massive damage to the area and left some people homeless.
