A shopper was seriously injured when a car drove into "several people" at a supermarket, police have said.
A blue Citroen C3 hit pedestrians and drove off from the car park at Tesco in Harefield Road, Rickmansworth just before 14:00 GMT on Sunday.
A woman was taken to Watford General Hospital with serious injuries while a man was treated for slight injuries, Hertfordshire Police said.
Officers are trying to find the vehicle and its occupants.
Police said they believed the driver and a passenger were involved in an incident inside the store moments beforehand, where a person was challenged by Tesco security staff after allegedly attempting to steal alcohol.
The force has appealed for witnesses.