A police probe is underway after a woman collapsed in a field and woke up to find her lower clothing pulled down.
It is not known how the woman ended up face down in the field in Armthorpe while she was walking her dog.
She told police that she was walking in a park close to Fiddlers Drive and Fair Home View at around 3.55am on Saturday when she lost consciousness.
When she came round she had a slight injury to the right side of her head but no other injuries.
She said nothing was stolen while she was unconscious.
A police spokesman said: “Although the injuries to the woman’s head are minor and did not require hospital treatment, we are concerned about the state in which she found herself and are treating the incident as unexplained.
“The woman has absolutely no idea of how she came to be on the floor or what happened in the moments before she came round.
“She does remember seeing a man, around three metres away from her, who was walking a small white dog, but nothing further.
“We are keen to speak to this man or anyone at all who was walking their dog or walking through the park around this time on Saturday, so we can determine what has happened.”
Officers have carried out house-to-house enquiries and are keen to hear from anyone who was in the area at the time.
Anyone with information should call South Yorkshire Police on 101 quoting incident 195 of June 11.