Repairs to the Christchurch water supply have been set back by Wednesday morning's aftershocks, which also knocked out power briefly to thousands of homes.
The city council says some of Tuesday's repair work has been undone, and more parts of the city are now without water.
But the city's water supply has been given the all-clear after three days of intense testing failed to find any contamination from Saturday's earthquake, making it unnecessary to boil water. Canterbury Medical Officer of Health Alastair Humphrey says 500 water samples have been tested.
Power company Orion says about 30,000 customers were without power following the big aftershock, but that number is down to 200.
The 5.1-magnitude shake about 8am was followed by another aftershock in the afternoon measuring 4.1 on the Richter scale.
Magnitude 6 shock not unlikely
Civil Defence has warned that further aftershocks are expected and that an aftershock as powerful as magnitude 6 can be expected.
And Civil Defence Minister John Carter told Parliament on Wednesday that the recovery would take months rather than weeks.
Mr Carter says the demands for welfare will grow as people staying with friends or family move on, and it's likely more welfare centres will be needed. He says the quake and aftershocks are putting huge pressure on people, and the trauma is difficult for people to understand unless they have personally experienced it.
Onno Mulder, chief executive of council-controlled contractor City Care, says he expects supply and wastewater problems to continue for at least six months. Mr Mulder says some streets have had up to 15 breaks in their water mains.
State of emergency extended
The aftershocks come as a state of emergency in Christchurch was extended by seven days. The order, declared on Wednesday, relates to the city only, not the wider Canterbury area. Mayor Bob Parker says the move is essential for the city's ability to recover.
Curfews in the central city, from 7pm till 7am, were in place on Sunday and Monday.
Teams assessing the safety of buildings are starting to shift their focus away from the central city into urban areas.
Christchurch airport was not affected by the first aftershock. Terminal buildings did not sustain any damage.
Christchurch hospital says it has treated several people with minor injuries.
Telecom says there are some outages but most phone services should be working. It asks people to limit the amount of photo and video data they send on mobile phones to keep the pressure off services.
Passenger services disrupted
KiwiRail says its South Island passenger services were disrupted by the aftershock. The Picton-bound Tranz-Coastal service, which left Christchurch before the aftershock, was delayed in Rangiora and will be late arriving in Picton.
The Greymouth-bound Tranz-Alpine service was scheduled to leave Christchurch on Wednesday morning but has been replaced by buses.
The Palms shopping centre in the suburb of Shirley has closed following the aftershock, as have two Countdown supermarkets in Christchurch.
Nine Countdown supermarkets in the region suffered minor stock damage and are still open. However, the Colombo St and Ferrymead Countdowns shut their doors.
Selwyn District Council says it's checking roads, bridges and buildings in the region following Wednesday morning's aftershock.
