Police are investigating a collision in Chelsea Heights last night where a child sustained critical injuries.
It is understood a white van was travelling west on Thames Promenade, near the intersection of Mulkarra Drive, when it struck a toddler about 9.10pm.
The child was on a small balance bike using the pedestrian crossing, with a man who was walking.
An off-duty police officer stopped to assist the child, who was then worked on by emergency services at the scene.
The child was transported to hospital with serious injuries and remains in a critical condition.
The man who was walking across the road was not injured.
The male driver of the van stopped at the scene and was arrested.
The 29-year-old Clyde man was interviewed and released pending further enquiries.
Major Collision Investigation Unit detectives are working to establish the exact circumstances of the collision.
Anyone who witnessed the incident, with CCTV/dashcam footage or any information that could assist police is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au