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
A head teacher has apologised for a “failure” which saw a child left behind on a school trip to London.
A look ahead at the forecast for the Tyne Tees region.
The Cullercoats Lifeboat crew were alerted just before 5pm to a man in difficulty in the sea.