A series of events is being staged in Wrexham to commemorate the 75th anniversary of a mining disaster which killed 266 men.On 22 September, 1934, an explosion - possibly caused by a spark off a tool - ripped through Gresford colliery. An air raid siren sounded in the town at 1100 BST, while Wrexham FC will play on Tuesday in commemorative shirts and will release 266 black balloons. Albert Rowlands, 89, is thought to be the last survivor of the gas blast.