Britons among miners caught in gas explosion

(EPA)

As many as four Britons are thought to be among 29 men believed trapped underground following a gas explosion in a New Zealand coal mine.

As families stood vigil and rescuers waited to find out whether the site was safe to enter, the chief executive of the Pike River mine, Peter Whittall, said that there were "possibly three or four" British workers underground, judging from passports.

Operators of the mine, in rugged mountains on the west coast of the South Island, feared that a power cut might have damaged the ventilation system, causing a potentially dangerous build-up of gas. Air quality tests were carried out as they prepared to launch a rescue operation.

Several hours after the blast yesterday afternoon, five men came to the surface with minor injuries. But with communications cut, it was unclear in what condition the remaining miners were – or whether they were even alive.

Tony Kokshoorn, mayor of the nearby town of Greymouth, warned it could be days before rescuers were able to enter the mine. "We are holding onto hope. Look at Chile – they all came out alive," he said.

The explosion, at one of the country's largest coal mines, came about an hour after the start of the afternoon shift. Mr Whittall said the missing men were believed to be about 120 metres down, but up to 2.5 kilometres inside the mine, which is drilled into the side of a mountain. Television footage showed blackened trees nearby and smoke billowing from the top of a ventilation shaft. An adjacent hut had been blown down, indicating a powerful blast had shot up the shaft. Police said there could still be pockets of methane in the mine, with the electricity failure complicating efforts to pump air inside.

The five known survivors include a grader driver, Russell Smith, who was blown off his machine. He escaped largely unscathed and was taken to hospital, along with an electrician, Daniel Rockhouse, who had been called in to investigate the blackout. Mr Smith's sister, Glenda Brown, said her brother had no recollection of what had happened.

A police spokeswoman, Barbara Dunn, said rescuers were "itching to get in there and start looking... [but] they can't just go charging in there and put other people at risk".

According to the country's Energy Minister, Gerry Brownlee, there has been no contact with the miners since half an hour after the blast. It was not clear whether they would be able to access emergency exit tunnels.

The coal seam is reached via a 2.3-kilometre horizontal tunnel. It was not known at what depth the explosion happened. After Mr Smith and Mr Rockhouse emerged, three other men walked out unharmed. One of the latter had been able to make a call on his mobile phone before reaching the surface.

Mr Whittall said the horizontal tunnel would make the rescue effort easier. "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."

Pike River, which has been operating for two years, is located not far from the site of one of New Zealand's worst underground disasters, an explosion that killed 19 people at the Strongman Mine in 1967.

* One of the missing Britons is understood to be Pete Rodger, 40, from Perthshire in Scotland.

The former Perth Grammar pupil emigrated to New Zealand two years ago to be closer to his mother and sister who live there, according to the Courier newspaper. He was formerly an offshore oil engineer.