Mystery surrounds the death of a woman found unconscious in a supermarket car park in west Hull.
The 38-year-old, from Hull, was discovered behind the Netto store, Anlaby Road, near to Boothferry Park, on Saturday morning.
She was taken to Hull Royal Infirmary but was pronounced dead at 2317 BST.
Humberside Police say the post-mortem examination of the woman has proved "inconclusive".
Officers are now trying to piece together the woman's movements in the hours leading up to her being found unconscious.
She is described as white, with dark collar-length hair and was wearing a green fleece, jeans and black shoes.
Anyone with information is asked to contact police in Hull.