At 2.30pm on Wednesday, March 23^rd, 1887, an explosion in the mine blew out of the tunnel mouth carrying with it an unconscious boy, Herbert Cope. Eighty one bodies were recovered and subsequently buried at St. Augustines Church of England, with eight at Fairy Meadow Roman Catholic cemetery (Corrimal), some at Woonona churchyard and the unidentified at Bulli. 

Bulli Colliery was a "gassy" pit having high concentrations of "firedamp" (methane) within its coal. Bleeding off into the mine workings, this gas was diluted and removed to the surface by the circulating air of the ventilation system before it accumulated and formed an inflammable mix (methane is inflammable within the approximate range of 5 - 15% when mixed with air so the object is to maintain the gas concentration well below the 5% level).

The source of the explosion was in the "Hill End" headings, known to be gassy and subject to gas "blowers". Not helped by the fact that the men working these headings had become casual towards the presence of gas and compounded by a deputy who apparently tolerated the use of unlocked lamps in contravention of "The Coal Fields Regulation Act", regulations that required all gas to be reported immediately to management and that locked oil flame safety lamps be used in gassy mines.

Although oil flame safety lamps were in use at the time, it apparently was common practice to remove the safety gauze from around the flame to permit more light from the lamp as this was the miners' only light source. In addition shots were being initiated by lighting the fuse from the open flame of the lamp or by matches.

The special commission and jury was quite scathing in its findings blaming both the miners and management for their attitude towards safety. Even the Government Inspector of Mines showed a lack of information as to what was happening at the mine.

The conclusion reached by the commission was "that the explosion was caused by marsh gas or carbonic hydrate that had accumulated at the face. That the immediate cause was probably the flame from an overcharged shot fired by a miner in the coal in No. 2 Heading." This gas explosion propagated a coal dust explosion and travelled towards the fresh air at the surface. The commission was also of the opinion that the Deputy, Overman and to a lesser extent the Manager, were all guilty of contributing negligence.

The last surviving widow died in 1942 and the sole survivor, Herbert Cope, died in 1952, aged 84.