An explosion of the mine occurred at 09:20 on Thursday 18 June 1885. Higson's report (read into the record of the inquiry by the coroner) explains that the explosion must have originated at the extremity of number 2 East level. The explosion was compounded by gas being sucked out of the large goaf beyond the eastern workings. The mine was acknowledged to be dusty by Hall and the roadways had to be watered to control this. Coal dust was implicated in the blast: "the props being coated thickly in some instances with coked or burnt coal dust". The white metal above the goaf was weak and in the large unsupported span ( by ) formed a bridge which fell away from the stronger Trencherbone rock. Within this space, firedamp was accumulating, undetected by the firemen's checks. At the time of the explosion a crack in the overburden opened up and the gas escaped to where men were working at the end of number 2 East. A naked candle ignited the gas. This initial blast would have been insufficient to explain the devastation. Higson's report supposes that the initial blast sucked more gas into the explosion and propagated it throughout the mine. Other contemporary and later research implicated coal dust as the culprit. Sir William Galloway (an Inspector of Mines and later Professor of Mining at the University College of Wales) was of the opinion that "the explosions are chiefly or very largely promoted by coal dust".