A cyclist's head injury has meant she is unable to remember if she was knocked down in a hit-and-run or if she just fell.
Lothian and Borders Police are appealing for witnesses to the incident at the junction of Easter Road and Dalmeny Street in Edinburgh on Tuesday.
The woman is thought to have been hit by a grey-blue car turning on to Dalmeny Street from Easter Road.
The 27-year-old was taken to Edinburgh Royal Infirmary at about 0830 BST.
The woman is also being treated in hospital for a fractured collarbone.
It is understood the car then drove west towards Leith Walk having failed to stop at the scene.
A number of people who stopped to help the injured woman are being urged to speak to the police.
A police spokesman said: "Officers are still trying to determine whether or not the woman has been injured as a result of just a fall, or whether or not the car actually struck her.
"To aid our investigation, we would urge anyone who was in the area and witnessed the incident or who can provide us with a more detailed description of the vehicle that failed to stop to contact police immediately.
'We are also particularly keen to speak to the driver of the car and would ask that they make themselves known to police and assist us with our enquiries."