But the rescue was hampered by further pockets of explosive gas.

Calcium carbide can react with water to create a highly explosive gas, which has led to speculation that water from fire hoses could have instigated the blasts.

It most commonly develops during an explosion, when molecules of air accumulated at the wave front are shoved together by the explosive gas urgently expanding behind them.

The situation worsens when it's discovered that there are a large number of explosive gas canisters on the site, directly in the path of the rapidly spreading fire.

As the coal workings became deeper, ventilation was a major problem, especially in seams giving off large quantities of the highly explosive gas methane.