The lawyer for former Pike River Coal chief executive Peter Whittall wants the Royal Commission into the mine disaster reconvened to hear three previously unheard witnesses.
Twenty-nine men died after a series of explosions in the West Coast coal mine that began on 19 November 2010.
Lawyer Stacey Shortall wants evidence heard former technical staff member, Udo Renk, and middle managers, Terry Moynihan and Greg Borichevsky.
She says the commission has been asked to reconvene the hearings to include statements from the three men.
"Mr Renk filed an earlier statement that was in the commission process, that was referred to I think on several occasions by other lawyers as they cross-examined people but Mr Moynihan and Mr Borichevsky did not file any statements during the course of the hearing."
Pike River families spokesperson Bernie Monk says the men's information could be vital to the outcome of the inquiry.
However he says their evidence could be taken without the entire commission having to reconvene.
The Royal Commission completed its hearings into the disaster in April.
It is due to report to the Governor-General by 28 September.