Billowing black smoke filled the streets of Wellington after a fire broke out on the roof of a high-rise building.

A loud bang notified workers that a 14-storey central Wellington building had a rooftop fire.

Shortly before 9am on Wednesday, smoke could be seen billowing from the Willeston Centre on the corner of Willeston and Victoria streets.

By 9.30am the fire, in a top floor machine room, was under control.

STACEY CAMPBELL Smoke coming from the roof of the central Wellington building.

Fire and Emergency New Zealand Wellington acting area commander Dave Key, who was at the scene, said the fire started in a service room on the rooftop, but could have spread if it had not been quickly brought under control.

There was a lot of smoke, but not too many flames, he said

While nobody was injured, one man on crutches needed help getting down from one of the upper floors.

TOM HUNT/STUFF Smoke is coming from the top of the building.

Johnny Tuivasa was installing air conditioning on the 10th floor when there was a "big bang" from above.

"We came running down to see all the smoke coming out."

Alex Rider, who was on the ground floor, said the thick smoke smelled like a bonfire.

STUFF The fire is on Willeston St.

Aaron Barsanti, who works at Cisco, three storeys from the top, assumed it was a regular smoke alarm.

But once he got outside he saw the black smoke billowing from the roof.

David Pettengell, who owns some floors in the building, including the top floor, said he was not in the building or in the area when the fire started.

He did not immediately know which floors were affected.

Victoria St remained cordoned off with emergency services at the scene.

The 14-storey tower complex on Willeston St was built by the Colonial Mutual Life Insurance Company in the 1980s.

In JunePettengell said the ceiling on the penthouse floor had been upgraded to meet 100 per cent of the new building standards, but the entry to the tower met 85 per cent of the code.

The air conditioning system had been overhauled on the floor, the walls had been repainted and new carpet tiles laid, he said.

The floor was configured as an open plan with a meeting room, a well-equipped kitchen and two bathrooms that both have showers.

The floor had room for up to 40 workers, he said.