Police are investigating reports of a couple having sex at a train station in full view of others.
The alarm was raised after a mum apparently learned one of her teenage children had witnessed the incident in Taff's Well, Rhondda Cynon Taf.
It is claimed that a man and a woman in their 20s arrived at the station on bikes on Saturday night before allegedly having sex.
British Transport Police confirmed it is investigating.
A spokesman said: "British Transport Police received a report of outraging public decency at Taff's Well railway station on the morning of Sunday 4 October, with the incident reported to have happened the night before at around 10pm."
Officers are appealing for anyone with any information to contact them.
Taffs Well railway station is on the Merthyr and Rhondda lines with up to six trains an hour going to Cardiff Central.
