People in two cars may have witnessed an unsolved chemical attack on a bus driver that left him with burns to his eyes and face south of Brisbane.
The liquid was thrown at the 35-year-old man through the driver's side window of the bus on Drews Rd, Loganholme, about 9.30am on Monday.
He was treated by paramedics and taken to Princess Alexandra Hospital, but no passengers were on the bus and no one else was injured in the attack
The Queensland Ambulance Service said the substance was a "chemical irritant".
Police are appealing for people who were in two cars - a white Mitsubishi Triton and a blue Hyundai hatchback - which drove past the scene to come forward.
"At this stage there is no suggestion the occupants of the vehicle were involved in the incident, however, they may have information that could assist with the ongoing investigation," officers said in a statement on Friday.