A man is wanted by the police for exposing himself to women on trains travelling through Sheffield and Chesterfield.
Three incidents have been reported on trains travelling between Leeds and Loughborough, which stop at Sheffield, Chesterfield, Nottingham and East Midlands Parkway.
On each occasion a man wearing shorts boarded the train then sat opposite lone females on the train before exposing himself.
Officers have released a CCTV image of a man they believe could hold vital information about the incidents.
They suspect there could be more victims.
Sergeant Roy McMicheal, of British Transport Police, said: “We believe that the man may regularly travel up and down the Leeds to Loughborough stretch of line which passes through Sheffield, Chesterfield, Nottingham and East Midlands Parkway, so it may be that there are other victims that we are unaware of.
“If you recognise the man pictured please contact us.
“We take all reports of this nature very seriously and our recent Report It to Stop It campaign, which aims to combat unwanted sexual behaviour on the railway by encouraging members of the public to report it, is proving very successful in supporting victims and bringing perpetrators of these crimes to justice.”
Anyone with information should call British Transport Police on 0800 40 50 40 or Crimestoppers, anonymously, on 0800 555 111.