NZ rescue chief promises to 'bring miners home'
The police chief heading the effort to rescue 29 men missing in New Zealand following a mine explosion has vowed to "bring them home".
Superintendent Gary Knowles said they had to ensure the site was safe before sending rescue teams below ground.
There has been no contact with any those missing at the remote coal mine on New Zealand's South Island.
Officials said there were 29 miners unaccounted for, two more than previously thought.
Earlier, two workers walked out of the mine with moderate injuries.
A company official earlier said that five men had come out of the mine, based on information from the two who came out, but there has since been no sign of the other three men.
"Our primary focus over the next 24 hours is to to hopefully locate the miners and bring them home safely," Mr Knowles said at a news conference.
"One of the key things we are facing at the moment is that the environment is somewhat unstable.
"I'm not prepared to put crews down below underground until we can stabilise the environment and it's safe to go in".
There are concerns about the possibility of another explosion, which is delaying the search effort, officials say.
There were also fears that ventilation in the mine may have been compromised due to an earlier power outage, hindering attempts to pump fresh air in, said police spokeswoman Barbara Dunn.
She said rescue teams were prepared and were keen to begin the search once they received the all-clear.
"They're itching to get in there and start looking for other people and a bit frustrated at having to stand and wait," she said.
The missing workers range in age from a 17-year-old - believed to be on his first shift - to a 62-year-old.
Most are New Zealanders but there are a number of Australian and British nationals among them, police said.
Each miner carried 30 minutes of oxygen, enough to reach oxygen stores in the mine that would allow them to survive for several days, officials from Pike River Coal, the mine operators, said.
'Hanging on to hope'
Peter Whittall, chief executive of Pike River Coal, said he hoped the miners were safe and sitting next to one of the air vents.
"It's quite conceivable that there is a large number of men sitting around the end of the open (ventilation) pipe, waiting and wondering why we are taking our time to get to them."
Earlier, Greymouth Mayor Tony Kokshoorn told the BBC that the friends and relatives of the missing miners were "hanging on to hope".
"We're just consoling them at the moment. We're setting up places for them to go," he said.
"We're all hoping that everything will turn out all right, but it's looking pretty serious at the moment."
The explosion at the Pike River mine is believed to have happened at around 1530 local time (0230 GMT).
The mine, which employs some 150 people, has been operational since 2008 and runs deep under the Paparoa Ranges on the rugged western coast of the South Island.
An electrician went into the mine at 1550 to investigate a power failure, and 1,500m (4,920ft) into the shaft he discovered the driver of a loader who had been blown off his machine. He then raised the alarm.
Mining experts said it could have been an explosion of methane gas, coal dust, or a combination of the two.
The last mining disaster to occur in the country was in 1967 at a mine called Strongman, close to Pike River, where an explosion killed 19 miners.