Detectives investigating two rapes in Sheffield taxis have been unable to find the alleged culprits.
In the early hours of May 12, last year, a 19-year-old woman left the University of Sheffield students' union in the Western Bank area of the city and believes she got into a taxi, which took her to Broomhill.
It is alleged that sometime during the journey, the taxi stopped and the woman was raped.
In the early hours of October 23, last year, a 25-year-old woman was allegedly raped in the Duke Street area of Park Hill after getting a taxi from West Street in the city centre.
A 44-year-old man was arrested but never charged.
Detective Chief Inspector Steve Ashmore, of South Yorkshire Police, said: “Officers investigating the reported incidents have conducted in-depth and thorough investigations and we are now confident, all lines of enquiry have been extensively exhausted.
“We have a duty of care to anyone who reports a crime to us and will investigate any report thoroughly.
"Any new information we receive in connection with the incidents will of course be looked into and investigated.”
Anyone with information should call South Yorkshire Police on 101.