Drill breakthrough in NZ mine; robot finds helmet

A drilling team on Wednesday broke a narrow shaft through to the section of a New Zealand coal mine where 29 workers have been missing for almost six days, and was greeted by a blast of potentially deadly gases from inside.

Officials have become increasingly pessimistic about the chances of pulling the men alive from a network of tunnels some 1 1/2 miles (2 kilometers) deep in the side of a mountain, following a powerful explosion on Friday.

Nothing has been heard from the missing miners since the blast. Toxic and potentially explosive gases have kept rescuers from entering the mine, though an army bomb disposal robot crawled two-thirds of a mile (1 kilometer) into the tunnel on Wednesday and found a miner's helmet with its fixed light still glowing.

Drillers using a diamond-tipped drill bit to prevent sparks finished boring a 530-ft. (162-meter) hole to the mine's main tunnel, close to where the missing men are believed to have been at the time of the blast. It was a key step, giving officials their first information from that section of the mine and allowing testing for levels of dangerous gases.

Hot air and gas rushed the hole when the chamber roof was punctured, and Pike River Coal Ltd. chief Peter Whittall said initial tests showed it was "extremely high in carbon monoxide, very high in methane and fairly low in oxygen." Carbon monoxide — the polluting gas from car exhausts — is extremely poisonous, while explosive methane is the gas believed to have ignited in Friday's blast.

"The environment is still unstable, it is unsafe and it is not appropriate to send rescue teams underground at this time," said Gary Knowles, the police superintendent in charge of the rescue operation.

Whittall said the helmet that was spotted by the robot belonged to one of two miners who were not as deep inside as the missing workers and who stumbled to the surface with minor injuries shortly after the blast.

He said it offered a small hope that if any of the missing miners had survived, they may not be in complete darkness.

A second robot had been sent into the mine, and a third was being prepared. Only the third robot has the capacity to explore deep enough into the mine to potentially spot the miners, officials said. Rescuers also plan to feed a camera down the bore hole.

Prime Minister John Key has warned the nation to prepare for the worst, as frustration among some relatives of those missing builds.

"We've got to know, we've got to go and have a look," Geoff Valli, whose brother Keith, 62, is missing, told National Radio. "Around town a lot of guys are prepared to go in and do it. It's time for men to do what men have got to do."

Knowles said he can understand the mounting pain of the families, but safety for rescuers is paramount and the dangers — including that of another explosion — were too great.

Security footage of Friday's blast shows a wall of white dust surging from the mine entrance and small stones rolling past for about 50 seconds as the force of the blast rips out of the mine. The dust was blown across a valley and the blast wave shot up a ventilation shaft, tearing off surface vents hundreds of feet above.

New Zealand's mines have been safe historically, with 181 deaths in 114 years. The worst disaster was in 1896, when 65 died in a gas explosion. Friday's explosion occurred in the same coal seam.

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Lilley reported from Wellington, New Zealand.

(This version CORRECTS Rewrites first lines and adds new details, quotes and photos. Trims outdated material. Corrects mine chief's comment on gas to carbon monoxide from carbon dioxide. An interactive with a gallery of diagrams about the mine is in the newzealand_mine folder. This story is part of AP's general news and financial services. AP Video. For global distribution.)