CHRISTCHURCH (Reuters) - International rescuers intensified their search for earthquake survivors in New Zealand on Thursday, spurred on by reports of a faint female voice heard beneath a collapsed church, even as the official death toll of 71 looked certain to climb.
Specialist teams from quake-prone countries including Japan and the United States used sniffer dogs and listening devices in increasingly desperate efforts to find more survivors, two days after a strong tremor struck the tourist city of Christchurch.
Rescue teams rushed on Thursday to a small church after it was believed that a woman's voice had been heard -- the first sign in more than 15 hours that people might still be alive.
"We have an active operation underway at the moment to try and ascertain what's happening," fire rescue official Jim Stuart Black said, careful not to raise expectations among distraught onlookers awaiting news of trapped family and friends.
There have been several false hopes so far, with one TV broadcaster already suggesting that the voice heard on Thursday might have been another kind of sound, not a sign of life.
A newly arrived Japanese rescue team headed straight for the site of what is feared to be the deadliest single collapse -- a six-storey building where as many as 100 people, including 11 Japanese students, are believed to have been entombed.
Around 30 Japanese rescuers, in orange and blue overalls, gathered at the smoldering ruin for a morning briefing before heading into the pile of broken masonry, which had housed an English-language school on its third floor.
The team had three sniffer dogs. As they met, other rescuers carried out more bodies from the rubble and officials brought additional body bags to the scene.
"We have a big team and we are determined to help," Kai Jinnai told Reuters.
"It is up the New Zealand fire service how long we are here, but while we are here we are going to do our very best."
DEATH TOLL TO CLIMB
Operations at the so-called CTV building, which also housed a local broadcaster, faced the risk that a nearby 26-storey hotel tower could topple at any moment and bring other buildings down. The Grand Chancellor Hotel is already leaning badly.
"We do have to brace ourselves that while the official toll is 71, that number will rise today and tomorrow," Prime Minister John Key said in Christchurch, his home town and the country's second-largest city with a population of almost 400,000.
Rescue teams had worked through a second night under floodlights, but reported finding only bodies.
The last rescue was of a woman, Ann Bodkin, from a finance company building mid-afternoon on Wednesday.
The toll was previously put at 75 but officials revised that. "We are aware there are other bodies but we haven't got a number on that," Civil Defense Minister John Carter said.
He said early reports of up to 300 other people missing was speculation and it was not known how many were unaccounted for.
Around 2,500 people had been injured, 164 seriously.
Police said they were still holding out hope that people were still alive in wrecked buildings.
"Experts tell me that there are pockets within a number of these buildings, and providing people haven't been crushed there's no reason that we will not get people out of there," shift commander Russell Gibson said.
Rescue operations have focused on the city's central business district, which bore the brunt of the force 6.3 quake that struck early afternoon on Tuesday when streets and shops were filled with lunchtime crowds.
There are fears that a collapse of the 26-storey Grand Chancellor, one of the city's tallest buildings, might trigger a domino-effect and further hamper rescue efforts.
"It's incredibly dangerous...if it hits the ground it will create a significant shock wave," local mayor Bob Parker said.
The city has been shaken by more than 100 aftershocks, bringing down more debris. Roads are buckled and large pools of water have welled up from broken pipes and sewers.
In places, roads had collapsed into a milky, sand-colored lake beneath the surface, the result of Christchurch's sandy foundations mixing with subterranean water under the force of the quake. Officials call it "liquefaction" of the ground.
Investment bank J.P. Morgan estimates the quake could cost insurers $12 billion, while catastrophe modeling firm AIR Worldwide Estimates says the insurance industry faces claims of NZ$5 billion ($3.5 billion) to NZ$11.5 billion ($8 billion).
Key said on Wednesday the estimates could neither be backed up or dismissed, but said the country could afford to rebuild the city although it would impact on near term economic growth.
Authorities said the arrival of more rescue specialists from Japan, Taiwan, Australia, Singapore and the United States would allow an expanded, intense search of three square km of the central city which is littered with flattened buildings.
More than 1,000 workers are expected to comb though shattered Christchurch buildings on Thursday.
A national state of emergency has been declared and the central city has been under curfew with soldiers patrolling in armored personnel carriers.
Thousands of people spent a second night in emergency shelters set up in local schools, sports grounds, and at a race course. Fresh water supplies were being distributed from schools and portable toilets set up as services were disrupted.