<a href="https://en.wikipedia.org/wiki/Ufa_train_disaster" id="mwAWI" rel="mw:WikiLink" title="Ufa train disaster">Ufa train disaster</a>: A <a href="https://en.wikipedia.org/wiki/Natural_gas" id="mwAWM" rel="mw:WikiLink" title="Natural gas">natural gas</a> explosion near <a href="https://en.wikipedia.org/wiki/Ufa" id="mwAWQ" rel="mw:WikiLink" title="Ufa">Ufa</a>, Russia, kills 575 as two trains passing each other throw sparks near a leaky pipeline.