Police have tonight confirmed an inquiry is underway into whether Pike River Mine evidence has gone missing.
1 NEWS last night revealed the door from an electrical control box was blown out of the mine in the 2010 explosion which killed 29 men.
Police say they're unable to speculate about the relevance of the item and are appealing to the public once again to come forward with any new information.
The man who headed the royal commission of inquiry, Sir Graham Panckhurst, told 1 NEWS this afternoon that to the best of his recollection, that piece of evidence was never presented at the hearing.
WorkSafe today confirmed to 1 NEWS that they don't have it.
The police still won't say if they do - a question we've been asking for four days.
It was non-certified, non-approved, but was the electrical device the ignition behind the deadly blast?
The cover of the box was blown out of the mine, but it doesn't appear it was used as evidence.
"It's a little disturbing that, to my recollection and it would seem to others' recollection as well, it didn't turn up at the royal commission in disclosure beforehand or during the course of the hearing," Nigel Hampton, royal commission lawyer said.
"If it can't be found then it is a concern," he said.
A former chief mines inspector from Britain, who's now advising the Pike families, has been trying to track it down.
A photo of the box cover was taken nine days after the explosion. He says it was then flown by helicopter to the Pike River office but hasn't been seen since.
And it may not be the only evidence unaccounted for, according to new claims. Fan blades and miners' equipment like gumboots are more evidence Pike families want answers on.