Police are asking anyone who saw a 13-year-old girl step off a moving bus in Cockburn to come forward.
The girl was on a privately owned bus travelling south on North Lake Road just after 3.30pm on Monday when she stepped off the back while it was still moving at low speed.
The teenager fell to the ground and knocked her head.
A woman travelling behind the bus stopped and helped the girl but she refused medical attention and asked to be taken to Cockburn Train Station.
Police say her health has since deteriorated and she's currently in hospital receiving treatment.
Crash investigators wish to speak to anyone who witnessed the incident, particularly the woman who assisted the victim and drove her to the train station.
Anyone with information or dash-cam footage of the incident is asked to call Crime Stoppers on 1800 000 333 or report online www.crimestopperswa.com.au.
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