The second explosion occurred at 2.37pm.
Had the atmosphere been right there could "possibly'' have been a rescue or recovery that first night, November 19, but the gas levels were not right, he said.
Firemen at the site, along with Mines Rescue, believed very early on that they were dealing with mass fatalities.
He said the police - also criticised during the commission of inquiry for filling all three main rescue roles - had a moral responsibility to consider all possibilities, including the possibility of survivors.
"Being in a position where you have to make ultimate decisions is extremely lonely. What was apparent very early on this was big, with a national and international dimension a role such as this required the influence of a big organisation (police).''
However, Mr Stuart-Black flagged to the police controller the need to consider "how far down the line you go before you make a decision''.
He was part of an expert panel in Wellington convened by the police five days after the blast to advise on the recovery effort.
Some people have already told the inquiry the best experts were actually at the mine site but they were not heard.
Mr Stuart-Black said the Wellington experts were not there to "pick apart'' the on-site experts but to flag omissions. Decisions were turned around "extremely quickly''.
However, one night the panel refused to sign off a risk assessment as it was "clear further work'' needed to be done.
Fire Service national commander Mike Hall, in a written brief today, said he issued an order to keep his men out of the mine.
Coal mines were particularly dangerous after a blast, and it would have been "reckless'' to send men down without full information on what was happening with gas levels.
The commission opened this morning with Justice Graham Panckhurst recording sympathies for the loss of four Welsh miners last week, when their mine pit was flooded.
"The agony of the search and rescue effort to follow ... and now we are learning something of the impact upon a small ...mining community. It is a pattern which is all too familiar.''
The Pike River families said they also stood squarely with the Welsh families.
"We know the shock and loss in this dangerous industry and the grief and the questions they will have,'' they said in a statement.
The inquiry continues.