WELLINGTON // An explosion ripped through New Zealand's largest coal mine today while about 30 people were underground, officials said. Five workers, dazed and slightly injured, stumbled to the surface hours later, while more than two dozen were missing.
Police said that shortly before the blast the electricity went out in the mine, which may have caused ventiliation problems. That may have contributed to a buildup of gas underground.
The explosion was powerful enough to blow one driver off his machine deep in a tunnel, and one mine safety expert said gas was a possible cause of the blast, although spokeswoman Barbara Dunn stressed it was too early to say why it occurred.
Rescue teams and emergency workers rushed by helicopter and by road to the mine, located in remote and rugged mountains near the town of Atarau on New Zealand's South Island. They cannot enter, however, before they make sure there is no gas buildup.
A police spokeswoman, Barbara Dunn, said: "They're itching to get in there and start looking for other people and a bit frustrated at having to stand and wait."
Tony Kokshoorn, the mayor of nearby Greymouth, told National Radio that it was unclear at what depth the explosion happened but that it was clear that it was very large.
Mr Kokshoorn put the number of miners unaccounted for at up to 30. Peter Whittall, chief executive of the mine's operator, Pike River Coal, said 27 people were missing, 15 miners employed by the company and 12 local contractors.
The coal seam is reached through a horizontal tunnel 2.3 kilometers in length that bores into a mountain toward the seam, which lies about 200 meters beneath the surface.
Mr Whittall said five workers had walked out of the mine: a pair that included the machine operator who was blown off his vehicle 1.5 kilometers into the access tunnel. Three more came out later. One of the men had been able to make a call on his mobile phone before reaching the surface, he said.
While the condition of the missing miners was not clear, the prospect that they could be alive but trapped recalls the dramatic saga of 33 Chilean mine workers who spent 69 days one kilometer deep in a collapsed gold and copper mine. They were rescued last month in an event played out on international television that captivated the world.
New Zealand's energy minister, Gerry Brownlee, said the explosion at the New Zealand mine happened at about 3.45pm (02.45 GMT) and the last contact with any of the miners was about half an hour later. They had not spoken to any of the missing miners during that time.
Two of the men who came to the surface were taken to a hospital for treatment of minor injuries.
Mr Whittall said: "They're being interviewed and we're trying to determine the full nature of the incident."
It was not immediately clear if all of those underground were together or in separate groups.
Mr Dunn said: "There is concern that ventilation inside the mine shaft may be compromised by the power outage."
A mine safety expert, David Feickert, said the blast could have been a gas explosion.
"There are different kinds of explosions that can occur in a coal mine - methane gas, coal gas and so on," he said. "If rescue teams can go in, that's good news indeed."
The St John Ambulance service said three rescue helicopters and six ambulances had headed to the mine. Rescue crews were assembled at the opening of the mine but had not yet entered as it was unsafe to do so until it was clear there was no buildup of gas.
Mr Brownlee said emergency exit tunnels were built into the mine but that he didn't know if they could be accessed by the miners.
According to the company's website, one vertical ventilation shaft rises 108 meters from the tunnel to the surface. This was blocked by falling rocks within the shaft in early 2009, delaying mining for months.
Mr Whittall said the horizontal mine tunnel would make the rescue effort easier than if the shaft was at a steep angle.
"We're not a deep-shafted mine so men and rescue teams can get in and out quite effectively, and they'll be able to explore the mine quite quickly," he said. "They will work throughout the night and they'll work until they can go right throughout the mine and determine the extent of the incident and the safety of our employees."
Pike River has been operating since 2008, mining a seam with 58.5 million tons of coal, the largest-known deposit of hard coking coal in New Zealand, according to its website.
Pike River says its coal preparation plant at the site is the largest and most modern in New Zealand and processes up to 1.5 million tons of raw coal a year.
The mine is not far from the site of one of New Zealand's worst mining disasters, an underground explosion in the state-owned Strongman Mine on Jan. 19, 1967, that killed 19 workers.