Authorities say they are investigating whether a three-year-old girl — who remains in a critical condition — was left on a bus for several hours in Gracemere, south of Rockhampton in Central Queensland.
Emergency crews were called to Gracemere just before 3pm.
The girl was located on the bus out the front of Le Smileys Early Learning Centre on Lucas Street.
Queensland police said she was found unconscious.
The Queensland Ambulance Service (QAS) said paramedics revived the toddler and took her to the Rockhampton Hospital, where she remains in a stable but critical condition.
QAS operations supervisor Jason Thompson said the three-year-old girl was unconscious when ambulance services arrived at the scene.
He said ambulance crews treated the toddler on the floor of the childcare centre.
"The child was unresponsive at that time," Mr Thompson said.
"The patient was treated, stabilised and transported to the Rockhampton Hospital."
He said Queensland police were already at the scene when they arrived. Officers are investigating the incident.
"When a child is sick, it's traumatic, and when one is as critical and unconscious, your heart goes out to them," he said.
The child's parents are at the hospital.