The expert panel concluded that the size and duration of the explosion indicated it was fuelled by a large volume of methane, perhaps up to 2000m3. Methane accumulated in the hydro goaf following mining was estimated at up to 5000m3. Another roof fall like that which occurred on 30 October 2010 would have caused a large pressure wave bearing a substantial volume of methane.
The pressure wave would have flowed down the hydro panel roadways and entered the main mine roadways, with the potential to flow inbye, particularly if a temporary stopping failed and allowed the wave to enter the main intake roadway. Methane carried along the roadways by the pressure wave would be diluted by air into the explosive range.
Another potential source of methane was an accumulation in the elevated inbye western areas of the mine. High methane readings were reported in these areas right up to the morning of 19 November.