It's her first time visiting the site.

"We've always had specialist advice that says it is possible to do a safe, manned re-entry and that's what we've committed to," Ms Ardern said.

Family members of some of the victims joined Ms Ardern, including Anna Osborne, who lost her husband Milt in the 2010 disaster. She's been a fierce advocate for re-entering the mine's drift to recover bodies.