Residents have been forced to leave their homes after an avalanche of mud slipped down a cliff and slammed into an Auckland apartment building tonight.

San Remo Apartments in Kohimarama Rd has been cordoned off after the hillside behind it gave way about 8pm following torrential rain in Auckland.

The fire service says large cracks are appearing on the hillside above the properties.

Emergency services raced to the scene and Urban Search and Rescue workers were digging through the mud and debris.

Initially the fire service believed a couple were mising but they have now been accounted for.

Police and the Fire Service confirmed all residents of the San Remo Apartments at 11 Kohimarama Rd are safe and well.

Earlier, Fire Service shift manager Daniel Nicholson said firefighters and an urban search and rescue team were searching in the dirt to find a resident missing from Apartment 7, which took the brunt of the landslide at about 8pm.

Craig Jones, a director of Visitor Solutions Ltd, is registered on the electoral roll at that address. His aunt Mary Jackson said he was "fine".

"His father has gone to pick him up because he can't get his car," she said.

'The most almighty crash'

A resident, Andrew Dwyer, who was in his apartment at the time, said he was eating dinner when an avalanche of mud swept down the cliff and smashed through his back door and windows.

"There was the most almighty crash and the front door burst open. It was forced open by a mudslide from the cliff behind the apartments," Dwyer said.

"Two neighbouring apartments are in exactly the same position, their front doors forced open, their windows smashed by the amount of mud that's come down the cliff.

"We think that everyone's safe. There is one guy who isn't in but we think he's probably out for the evening."

Shocked residents then fled the building before emergency services arrived.

Dwyer told the Herald two buildings had been cordoned off and the river of mud was believed to have hit another building.

The fire service had said the area was very dangerous. It was unlikely anyone would be allowed back into their apartments tonight so residents were making alternative arrangements to sleep.

Dwyer said the couple who was unaccounted for were believed to have been elsewhere when the mud slide hit, which was later confirmed by police and the fire service.

The apartments sit at the bottom of a bush-covered bank leading up to a large Catholic church property overlooking Mission Bay and Kohimarama Beach.

A Herald reporter at the scene says there are five fire trucks, three ambulances and four to five other St John vehicles.

She said emergency workers and Urban Search and Rescue crews were working on a cliff behind the building.

"They're all still up the cliff."

Police said reports were received at about 8pm that a hillside had collapsed onto a unit of flats between Eltham Rd and Tamaki Drive. The large slip was estimated to be 10 metres wide.

Staff were working to account for the residents in the building.

Service shift manager Daniel Nicholson said the landslip came through the apartment complex at 11 Kohimarama Rd.

"Apartment 7 is affected. One person from that apartment is unaccounted for," he said.

"The crews are using hand tools to pick through the dirt. Once our Urban Search and Rescue team, get there they will decide what needs to be done next."

All other residents in the block and in some neighbouring properties had been evacuated.

"We were told there were large cracks appearing on the hillside above other properties as well, so we are taking precautions," Nicholson said.

The collapsed cliff cannot be seen from the road, which has been cordoned off.

A small group of media have gathered in the rain to await developments.

Inspector Kerry Watson says at this point everyone is accounted for.

Fire Service shift commander Daniel Nicholson said he did not yet have official confirmation that the two missing people at Kohimarama had been found.

"We are still looking for two people at this stage."

There are seven units and emergency workers have gone through all of them.

Watson said no injuries had been reported. "There was a large volume of mud and it has broken a door down"

Police will remain at the scene of the slip in Kohimarama overnight where affected properties have been evacuated.

It does not appear that any further evacuations in the area will be necessary.

Police will maintain a presence to ensure the evacuated properties remain secure.

Nuns warned not to walk on paths

A community of 25 retired Catholic nuns and a 30-bed Catholic rest home above the collapsed cliff have been warned not to walk on the paths along the clifftop.​

Community leader Sister Colleen Woodcock said everyone on the property was safe.

"Luckily none of the older people were outside, it being such a foul night," she said.

"We do have paths out there. I'm just about to go and put signs up for the morning walkers."

She said the Fire Service had also told the sisters to stay out of an administration building housing the NZ headquarters of the Sisters of St Joseph, which is closer to the cliff than the nuns' residential quarters and the rest home.

About six staff who work in the building have been told not to come into work tomorrow.

- NZ Herald