It could take 15 years to rebuild the centre of Christchurch following last week’s devastating earthquake, New Zealand Prime Minister John Key said on Wednesday.

He said that one in three commercial buildings in the central business district, where more than 50,000 people used to work daily, may have to be demolished.

The centre, which has been cordoned off because of the continuing danger of falling masonry, could remain effectively closed to the public until Christmas, Mr. Key told the Newstalk ZB radio station.

The official death toll from the magnitude 6.3 quake on February 22 rose to 159 on Wednesday but police have said it could reach 240 and some bodies may never be recovered from the shattered buildings.

Civil defence officials began distributing face masks Wednesday as winds gusting to 90 kilometres an hour whipped up the silt lying in the streets since the quake into dust storms.

Officials said the quake brought an estimated 200,000 tons of silt to the surface and although volunteers, including 600 farmers from the surrounding countryside, had helped trucks to clear 214 streets, about 60,000 tons remained.

Mayor Bob Parker said that while the dust was not thought to be contaminated, anyone with a respiratory condition should wear a mask.

Residents were also warned not to swim in the sea which is contaminated with raw sewage and to continue boiling the water, which was unsafe to drink.

More In: International | News