The aircraft departed Bankstown on a flight to Waikerie at a cruising altitude of 8,000 ft. About 90 mins after takeoff the pilot selected the left and right auxiliary tanks to supply fuel to their respective engines. Some 68 mins later, when the auxiliary fuel tank contents had both reduced to about 20-25 lbs, the pilot turned the left engine fuel selector to the left main tank. One minute later, he turned the right engine fuel selector to the right main tank. Approximately two minutes later the pilot noticed a change in the tone of the left engine and felt a slight shudder through the airframe. The left engine began to run rough, which worsened until it lost all power and stopped, despite attempts by the pilot to restore engine power through the use of the auxiliary fuel pump and changes in mixture. Attempts to restart the left engine were also unsuccessful. The pilot transmitted a PAN report and commenced the left engine shutdown checks. However, the right engine commenced to run rough before it also suffered a complete loss of power, which could not be restored. The pilot transmitted a Mayday report and carried out a forced landing onto a field in the Malee National Park, approximately 25 NM east of Mildura. During the landing the aircraft suffered substantial damage, including a small fire in the right main tank, which the pilot was able to extinguish using a portable extinguisher. He then activated an emergency locator transmitter (ELT). By 1640 search aircraft had located the accident site with the assistance of ELT signals. Local police services attended the scene. The pilot subsequently discovered a substantial amount of white powder, later identified as sugar, in the auxiliary fuel tanks. As it appeared there had been some form of deliberate contamination of the fuel system, the police assumed responsibility for any further investigation.