GREYMOUTH, New Zealand (Reuters) - A pall of gloom hung over this small New Zealand town on Thursday as the government promised an independent inquiry to try to answer what caused the country’s worst mining disaster in nearly 70 years.

Flags flew at half mast under grey skies in Greymouth on the rugged west coast of the South Island in memory of the 29 miners trapped nearly a week ago, who police said would not have survived a second explosion in the Pike River Coal mine on Wednesday.

“The country is unified in its grief and hopefully it will give some comfort to the families that have been left behind,” Prime Minister John Key told Radio New Zealand, adding that an independent inquiry would be held in addition to probes by the Police, the Labour Department and Pike River Coal.

“We need answers to what happened at Pike River. We owe it to those families,” he said.

The 29 miners were trapped in the 2.3 km (1.4 mile) main tunnel last Friday night when methane gas caused a massive explosion in the mountain. Two other miners working away from the coal face narrowly escaped and walked out of the mine.

On Wednesday, rescue teams had been readying to enter the mine and were reviewing deadly gas levels which had stopped them entering the mine, when the second gas explosion occurred.

The miners’ relatives had pleaded for rescue teams to enter the mine to find their husbands and sons.

A combination of undated pictures released by the New Zealand Police shows 27 of the 29 miners trapped inside the Pike River Coal mine. All 29 miners trapped underground for five days are believed to be dead following a second explosion in mine, police said on November 24, 2010. The miners are (top row L to R) Conrad John Adams, 43, Malcolm Campbell, 25, Glen Peter Cruse, 35, Allan John Dixon, 59, Zen Wodin Drew, 21, Christopher Peter Duggan, 31, Joseph Ray Dunbar, 17, John Leonard Hale, 45, Daniel Thomas Herk, 36, (second row L to R) David Mark Hoggart, 33, Richard Bennett Holling, 41, Andrew David Hurren, 32, Jacobus (Koos) Albertus Jonker, 47, William John Joynson, 49, Riki Steve Keane, 28, Terry David Kitchin, 41, Samuel Peter McKie, 26, Michael Nolan Hanmer Monk, 23, (bottom row L to R) Kane Barry Nieper, 33, Peter O'Neill, 55, Milton John Osborne, 54, Brendan John Palmer, 27, Benjamin David Rockhouse, 21, Peter James Rodger, 40, Blair David Sims, 28, Joshua Adam Ufer, 25 and Keith Thomas Valli, 62. REUTERS/New Zealand Police/Handout

There had been no contact with the trapped men, and robots and electronic devices used to explore the mine found no signs that any had survived the initial blast.

The mayor of the Grey District said the disaster was the region’s “worst hour,” but families needed to retrieve the bodies of the miners.

“We’ll get someone down that mine, we’ll get those bodies back because these people won’t have closure,” said Tony Kokshoorn.

The Pike River mine, on the sparsely populated west coast of the South Island, is close to the site of New Zealand’s worst mining disaster, where 65 miners were killed by gas in the Brunner coal mine in 1896.

The father of one of those killed, who had been outspoken about the way the rescue effort was handled, said he would not rest until he got answers.

“I’ll make sure of that...it doesn’t matter how long it takes, I’ll get the truth,” said Laurie Drew, father of 21-year-old miner Zen.

Around 200 people, including one of the survivors, miners’ families and the mine company’s senior executives, attended a church service on Wednesday night to mourn.

The scale of the disaster, the greatest loss of life from one event in the country of about four million since the Wahine inter-island ferry sank more than forty years ago, is reverberating across the nation.

The New Zealand stock exchange said the market would open five minutes late as a mark of respect for the disaster.

Authorities are believed to be looking at pumping inert gases such as carbon dioxide and nitrogen in the mine to put out any fires inside the mine before making any attempt to recover the bodies.