Thirty-three people were on board a Greyhound coach when it collided with a four-wheel-drive towing a caravan on the Bruce Highway on June 30.
A 56-year-old woman from Townsville died in the crash.
The two others killed were women from Germany, one in her 20s and the other in her 30s.
Four men were hospitalised, including a 24-year-old man in a critical condition and a 23-year-old man in a serious but stable condition.
A 27-year-old man and a 51-year-old man were in a stable condition.
The driver of the bus, a 56-year-old man, and the driver of the Landcruiser, an 83-year-old man, escaped without injury.
Police are appealing to nearby motorists as the investigation into the crash remains in its infancy.
The crash happened near the Wilson Creek rest area on the Bruce Highway at Gumlu, which sits on a stretch of highway between Bowen and Ayr.
Police are interested in speaking with the driver of a white utility who was believed to have been travelling behind the bus prior to the collision.
Anyone with information or relevant footage is also urged to contact police.
