New blow in mine rescue mission after tunnel robot breaks down

Police superintendent Gary Knowles said the army robot sent in to transmit pictures and assess toxic gas levels was damaged by water and out of commission.

Authorities were urgently seeking other such robots from West Australia and the United States to replace the broken one, Mr Knowles said.

"I won't send people in to recover a robot if their lives are in danger," he said. "Toxicity is still too unstable to send rescue teams in."

Making matters worse, the drilling team boring into the mine tunnel had hit "very hard rock" overnight, Mr Knowles said.

The police superintendent's statements came as rescuers waited impatiently for a chance to test if air quality underground was safe enough for them to go in to pull out the miners, who have been trapped for nearly five days.

Scots Pete Rodger, 40, from Perthshire, and Malcolm Campbell, 25, from St Andrews, Fife, are among those missing after a fireball ripped through the Pike River mine in Atarau on the South Island on 19 November. Family members have expressed frustration with the pace of the response as officials acknowledge it may be too late to save the miners

• Scots Pete Rodger, left, and Malcolm Campbell are among those missing

A build-up of methane gas is the suspected cause of the explosion. And now the presence of that gas and others – some of them believed to be coming from a smoldering fire deep underground – are delaying a rescue over fears they could still explode.

David Seath, secretary of the Mining Institute of Scotland, said: "The biggest problem they (the rescue teams] have got is that they are going to have to work in a contaminated atmosphere that has gases that are either explosive or noxious.

"Methane is a gas which explodes when the percentage reaches a level of five to 15 per cent, and carbon monoxide is a gas which can kill with a few hundred parts per million.

"There could be thousands of parts per million in a mine where there has been an explosion.

"What they will be hoping for is that the men are in an air pocket and won't be exposed to these gases but the risk is putting rescue workers into that atmosphere to try to recover the men that are down there."

A diamond-tipped drill was put to work as workers hit layers of hard rock and came within 33 feet (of the tunnel where they believe some of the miners are trapped, Mr Knowles said.

The 500-foot-long shaft they are creating will allow them to sample gas levels – including explosive methane and carbon dioxide – and determine if rescuers can finally move in days after the blast.

Mr Knowles said rescuers planned to drop a listening device down the hole to see if they could hear anything – such as tapping sounds – that might indicate that the miners were still alive.

"This is a very serious situation and the longer it goes on, hopes fade, and we have to be realistic. We will not go underground until the environment is safe," Mr Knowles said.

Two workers stumbled out of the mine within hours of Friday's explosion, but there has been no contact at all with the remaining 29. A phone line deep inside the mine has rung unanswered.

"The families are showing grief, frustration and probably anger," said Laurie Drew, whose 21-year-old son, Zen, is among the missing.

"I have my moments I can keep it together but deep down my heart's bleeding like everybody else's."

Those trapped include a teenager who was so excited about his new job he persuaded mine bosses to let him start his first shift three days early – on the day of the deadly gas explosion – his mother told local media.

Joseph Dunbar was one day past his 17th birthday and the youngest among them when he joined his fellow miners in the pit.

Mine shift supervisor Gary Campbell said Joseph was desperate to be part of the team. His mother, Philippa Timms, said her son "got offered this chance to have a career – and that's how he saw it, as a career," she said.

The wait to begin the rescue bid for the men had been frustrating, but Ms Timms said she understood why.

"They can't just rush in there because, I know right from the word go, I know how it works," she said. "If the oxygen rushes in and it hits that methane, then bam, they're gone, (in) another blast."

Police have said the miners, aged 17 to 62, are believed to be about 1.2 miles (two kilometres) down the tunnel.

Each miner carried 30 minutes of oxygen, and more fresh air was stored in the mine, along with food and water that could allow them to survive for several days, officials say.

New Zealand's mines are generally safe with a total of 181 people killed in the country's mines in 114 years.