Nearly nine years after 29 men were killed in a New Zealand coal mine explosion, authorities have taken the first steps back into the disaster site and begun a search for answers.

The families of victims killed in a series of methane explosions inside the South Island’s Pike River cheered and shed tears on Tuesday as they watched the mine being re-opened for entry for the first time since the November 2010 blasts.

Among those who died were Australians William Joynson, 49, and Joshua Ufer, 25.

The families of those who died have fought a long, complex battle to have the site re-entered to find the cause of the disaster and to recover the bodies of their loved ones.

In a small, private ceremony at the mine’s portal on Tuesday, relatives nervously watched as the doors were unsealed and a three-man team took the first symbolic steps inside, beginning what will be a months-long search of the 2.3-kilometre drift or entrance section.

They came out shortly after to cheers.

“This is the start of a journey that will end with truth and justice,” Anna Osborne, who lost her husband, Milton, in the disaster, said.

Any evidence found in coming weeks will be handed to police.

Family members are comforted at New Zealand’s Pike River coal mine site. Photo: Getty

The event came about two weeks after the families and New Zealand’s top politicians gathered at nearby Greymouth, only to have the reopening postponed at the last minute due to a spike in oxygen readings.

Instead, an optimistic but bittersweet ceremony was held at the portal on May 3.

Mr Ufer’s mother, Joanne, crossed the Tasman to be there that day and was joined by his daughter, Erika, who was born six months after the explosions.

Ms Ufer was unable to attend Tuesday’s event but said earlier that while the re-entry was a victory after a long, emotional rollercoaster, it was too soon to think of fulfilling her hope of taking her son’s body back to Australia.

“I had to reconcile, in my own head and my heart, that Josh would never be coming home … I reconciled with myself that the probability was next-to-nil and that’s the only way I’ve kept going,” she said.

“We’ve given it our all. We’re getting in there. And if we find evidence or we find remains, that’s a bonus.”

Re-opening Pike River was deemed too dangerous by the mine’s owner and the previous government in 2014 but New Zealand’s Labour Party pledged to try if elected.

On Tuesday, the minister in charge, Andrew Little, called the disaster a “corporate and regulatory failure”.

“Fulfilling the promise to do everything possible to safely re-enter is an act of justice for families who have waited for far too long,” he said.

“There is still much to do. We must find out what happened at Pike River.”

Intensive safety work, including pumping nitrogen into the drift, has been ongoing for months.

While no individuals were prosecuted over the disaster, former owner Pike River Coal was ordered to pay the families of the 29 men and two survivors a total $NZ3.4 million ($3.2 million).

Left in liquidation by the explosions, the company was unable to meet its obligation. Charges were dropped against Australian boss Peter Whittall after he volunteered to pay up in 2013, a decision that was later ruled unlawful.

-AAP