The newborn baby’s body was pulled from the river Taff near the junction of Penarth Road and Taff Embankment shortly after 6pm yesterday.
The body reportedly still had a placenta attached to it, suggesting that it had only just been born.
South Wales Police said that they would not comment on who found the body, or how.
They have, however, asked the public for any help possible in tracking down the little one’s mother.
Detective Inspector Paul Latham said: “We want to locate the mother of this baby to ensure she receives the medical attention she needs.
“We appeal to her to contact us, so that we can provide her with the support and reassurance that she requires.”
He added: “We want to hear from anyone who has any information concerning this incident or from anybody who may be able to assist us in identifying the mother of this baby who is believed to have been born within the last few days.
“Whilst this investigation is in its early stages, I want to stress that our priority is the safety and well being of the mother at this time.”
Anyone with information is asked to contact South Wales Police on 101 or Crimestoppers on 0800 555111 quoting reference 1500224381.