UPDATED 3.27pm A growing number of buildings in central Wellington are deserted as the full extent of quake damage in the capital begins to emerge.

LISTEN ABOVE: Wellington Mayor Justin Lester spoke to Larry Williams

An apartment block, a large office tower, the Defence Force headquarters, and the home of New Zealand's spy agencies are the latest buildings to be evacuated.

Simpl House on Mercer St, a mixed-use office tower, was evacuated about 10.30am today.

The building - which is opposite the council headquarters and central library - houses offices, retails outlets, Plunket and the Government drug buying agency Pharmac.

The Tennyson Apartments building on Tennyson St, Te Aro, was also evacuated this morning.

Fire Service Wellington assistant area commander Gareth Hughes said a main structural element of the Tennyson Apartments, which was holding up a fair bit of weight, had suffered a “severe crack”.

Council engineers had alerted firefighters after a routine post-earthquake check this morning. The Fire Service then assisted with evacuations.

“We’ve evacuated approximately 60 residents out of the building. There’s about 23 apartments.”

Police and Wellington Region Emergency Management staff had helped to find alternative accommodation and ensure the residents were safe.

The Fire Service would work with urban search and rescue and council engineers to assess evacuation zones and the immediate future of the building.

“We’ve evacuated buildings either side for safety. Life risk is our main priority.” 

Wellington Regional Emergency Management spokeswoman Janet Purdey said the main concern was still an office tower at 61 Molesworth St, which had suffered structural damage.

Wellington Mayor Justin Lester told a press conference this afternoon that engineers were still assessing the tower at 61 Molesworth St.

However, he added: “It’s likely it will need to be deconstructed.”

“Within two hours, we’ll know what that plan looks like, we’ll know what that process is likely to be.”

Lester said there would “not necessarily” be huge disruption as a result.

Lester said anybody evacuated out of the building on Tennyson street would have accommodation arranged for them if they had nowhere to go.

He said the assessment team initially found 60 buildings "that were of concern to us in terms of showing signs of structural damage".

They then identified about 28 buildings "at the risk of some part of the building . . . falling down."

General manager for the building consents team Mike Scott said public safety was "absolutely critical".

The exclusion zone around the building was one and a half times the building's height, which was "international best practice until you have full detail".​

The cordon in place around the building was extended this morning to include Pipitea House, on Pipitea St.

The building, which houses the Government Communications Security Bureau and the Security Intelligence Service, was only recently opened in 2011.

Purdey said there were concerns with its facade, especially with high winds expected later today.

Scott said they might be able to reduce the cordon depending on information they received about the building later today.

"We've got to be very cautious about how we do this, we can't put anybody at risk, but we are also critically aware of the impact this is having on the city and that area in particular.

"We're taking a very measured approach but we're doing it at real pace, and make sure that we're going to get things moving as quickly as we can."

Scott said the owner of the building had been "phenomenal" to deal with and had been working closely with them.

He said the owner was "comfortable with the process today".

The spy agencies have been approached for comment.

Other buildings within the Molesworth St exclusion zone, which are off-limits to occupants and the public, include:

• Royal Thai Embassy
• New Zealand Rugby Union headquarters building and the tenancies within, including NZ Post and Audit New Zealand
• Red Cross offices
• Wellington Cathedral of St Paul
• A number of private houses accessed off Collina Tce.

Alternative arrangements are being made for worshippers at Wellington Cathedral of St Paul, which is now formally closed.

The Defence Force today also confirmed its building - Freyberg House on Aitken St - had also been closed due to damage.

"The full extent of the damage will not be known for several days, and until that assessment is complete we cannot determine what work will have to be done or when it will be possible to reoccupy the building," a spokesman said.

"Consequently we are considering a range of options for interim solutions, including remote working and relocation of staff to other NZDF facilities.

"The safety of our staff and those who work with us in other capacities is of paramount importance and this will remain our primary concern in the coming weeks."

Not all of the evacuations have been ordered by authorities.

Purdey said the evacuations on Tennyson and Mercer streets had been ordered by the building managers.

Earlier today, one lane of Featherston St reopened to traffic after it was earlier closed due to falling debris.

Concerns about another building in Wellington early this morning turned out to be a false alarm.

The building at 40 Taranaki St was cordoned off just after 2am before being given the all-clear.

Other buildings closed by the quakes include Statistics House, which suffered structural damage including a pancaked floor.

The building was purpose built for Statistics New Zealand in 2005 and the agency recently signed a 16 year lease on the building, which is owned by CentrePort - a company owned by the Wellington and Manawatu-Wanganui regional councils.

Engineers have cleared Westpac Stadium of major structural damage, but the concourse and seating bowl will stay closed for around two weeks so damage, including liquefaction on the stadium's ring road and burst water pipes, can be repaired.

The 7.5 magnitude earthquake also cracked concrete and broke windows at the stadium.

- NZ Herald