Detective Superintendent Heather Pearson, of North Yorkshire Police said:
As a result of the incident a criminal investigation is underway. Officers are deployed to support the 83-year-old woman who is being cared for by family members.
"A number of enquiries are ongoing including tracing people who can assist.
"Detectives would like to speak to anyone who can assist in establishing a picture of the events leading up to the assault and ask that they contact York CID as soon as possible."
Any witnesses are being asked to contact North Yorkshire Police on 101.
More top news
Multi-platinum-selling rapper Tinie Tempah has announced a return to the North East for Marina Live.
Lifeboat crews saw an eight per cent increase in call-outs in 2016 and are urging people to be more aware of the dangers of the sea
Cases include a dog stamped on and thrown down stairs, and a dog who went blind through neglect. **Warning - contains distressing images**