Emergency services attended a Sainsbury's car park after a car overturned.
Police were called at 11.20am today (April 16) to the supermarket on Fox Den Road, in Stoke Gifford.
An Avon and Somerset Police spokesman said: "Officers attended and found one car was on its roof.
"Another vehicle reportedly involved had been driven away from the scene before emergency services arrived."
A picture from the scene shows a turquoise car on its roof, with an ambulance and two police cars nearby.
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Police were alerted to the incident by South Western Ambulance Service, which says it treated and discharged three patients at the scene.
“Enquiries, including reviewing CCTV footage, are ongoing," said the police spokesman.
“Witnesses are asked to call 101 and give reference number 5221081237."
