However, several sources have told the Greymouth Star that it was because Mr Monk and Mr Dunbar were focusing on the conveyor belt theory.
Mr Dunbar had claimed on national television that footage showed the conveyor belt moving at the portal before explosion debris came out of the mine tunnel, despite police advising that mine experts had concluded the belt was only moved by the force of the explosion.
Mr Dunbar went public again last month and claimed that an electrical cabinet, blown to the surface from inside the mine workings below, had been confirmed as missing by police.
Mr Monk said yesterday there was no split with the other families.
"Dean and I are working doing things on the side, but that's not influenced things."
The re-entry, which the Family Reference Group had worked to secure, was now happening: "That job has been done."
He did not want people to think he was "peed off".
"It's not quite like that. I've a good relationship with the agency, I've never had a fallout with them, and a relationship with the police."
This week Mr Monk was widely reported as saying he had stepped aside from the families group due to a confidentiality agreement over information from police.
Mr Monk did sign the agreement on the same day as the other members of the Family Reference Group.
He later clarified that after signing the agreement, some other family members had told him they were not comfortable with it, and it was important they were able to trust him.
- By Laura Mills