Australian bourse operator ASX falls on probe launch into certain practices

** Shares of ASX Ltd ASX fall 3.9% to A$69.92, their lowest levels since June 12

** Australia's bourse operator acknowledged investigation by the country's securities regulator

** The Australian Securities and Investments Commission (ASIC) launched an investigation into ASX's governance, capability and risk management practices

** Earlier in the day, stock hit its worst intraday drop since early April

** Stock up 7.3% this year, including the day's move