Civil Defence Minister John Carter says the state of emergency in parts of Canterbury is being extended to midday Thursday.
There were plans to lift the emergency in Christchurch, Waimakariri and Selwyn at midday on Wednesday.
But Mr Carter says the mayors in the affected areas have decided to retain the declaration.
Canterbury has been under a state of emergency since the magnitude 7.1 earthquake on 4 September.
Canterbury Civil Defence manager Jon Mitchell says the extension will give councils more time to deal with the status and protection of dangerous buildings, or those at risk.
He also says there may be a need for a further extension if there are any significant aftershocks.