According to Lincolnshire Police, the 48-year-old woman is currently in a ‘very serious’ condition at Hull Royal Infirmary.
A police spokeswoman said that there is ‘no indication’ that there was any crime involved, and that they are in the process of checking CCTV footage and speaking to witnesses.
Police are continuing to appeal for further witnesses after the woman was found at the junction of Upgate and Kidgate at about 12.30pm on Friday.
She was initially taken to Grimsby Hospital, before being transferred to Hull Royal Infirmary for specialist treatment.
Detective Inspector Simon Bromiley said: “We would like to hear from anyone who may have seen the woman in the area before she became injured, saw how she has become injured or stopped to help her following her injury.
“I am keeping an open mind, so any witnesses and any information that will help build a picture should please contact us on the 101 number.
“The female is described as 5ft 4 tall, medium build, wearing a brown coat and burgundy trousers.”