While cruising at 8,000 ft, enroute from Brisbane to Maryborough, the crew of the Shorts 360 aircraft heard a loud bang emanate from the left engine, followed by an increase in the engine's inter-turbine temperature indication. The crew shut-down the engine in accordance with company operating procedures and diverted for a landing at Maryoochydore. Following an initial inspection, the operator removed the engine and forwarded it to the manufacturer for an investigation and report. The manufacturer found that the engine's number 1 bearing had failed. The bearing balls and races exibited "spalling", and fatigue fracturing of the bearing roller cage was evident. The investigation report concluded that due to the severe secondary damage to the bearing assembly, the reason for the failure of the bearing could not be determined.