Pike River widow Anna Osborne says the families will release information that will shock the country in the coming weeks.
Ms Osborne said the families "possibly do have" the full 30 hours of police footage they have previously requested - but not obtained - via the Official Information Act.
Speaking on The AM Show on Monday, Ms Osborne said the information "will expose the Government and the cover-ups for what it is".
She stayed tight-lipped on precisely what information the families have, but let slip they've "seen quite a bit of footage from lots of different things, and this is just the start of things to come".
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What they have is "quite possibly" more revealing than the footage released by Newshub on Sunday, she said.
She says the footage released by Newshub shows the mine is safe for re-entry.
"What the footage shows is what the families have tried to convince the Government for a very long time - that the drift and its construction is not compromised at all by the explosions that have gone through.
"It is clear from the video footage that the drift is not in a bad state of repair and it can be re-entered and it can be done safely."
She said she is "gobsmacked" that the footage wasn't shown to the families and that it "reeks" of a cover-up.
"We have been waiting 6.5 years, and we've had no justice."
The Pike River families have the backing of Opposition parties, which are accusing the Government of withholding evidence.
But Prime Minister Bill English told The AM Show assessments have shown the mine is unsafe for manned entry, and decisions to re-enter the mine must be made according to New Zealand workplace safety laws.