Health officials in Christchurch are warning people with respiratory problems to stay indoors or wear a mask as strong winds are expected to kick up dust in the next 48 hours.
MetService is forecasting northeasterly winds to pick up in the next day to about 40km/h, with gusts reaching 90km/h by Wednesday.
Christchurch City Council says winds may whip up dust from quake-damaged buildings and the silt that has blanketed large parts of the city.
Canterbury Medical Officer of Health Alistair Humphrey says dust could cause breathing problems for those with asthma or other respiratory problems.
He says rescue workers will wear masks as they continue to search in the badly damaged central city.