Three people have been arrested in Cardiff after a baby was allegedly sold to a couple.
Detectives said the Spanish-born boy's mother had originally claimed he had died during an emergency operation at a UK hospital.
It has been reported that police in Spain believe the six-week-old may have been sold for up to £11,000.
A South Wales Police spokesman said: "Three people have been arrested in connection with an investigation into concerns for a baby in Cardiff.
"Two females aged 19 and 26 and a male aged 25 have all been released on police bail pending further enquiries.
"The six-week-old baby boy is safe and well and remains in the care of the local authority."
Spanish police alerted officers in Britain after suspicions were raised over the birth of the baby and the mother's claims he had died at the age of 15 days following an operation for an injury to a vein.
Her son - born in the Virgen de la Concha hospital Zamora in northern Spain in September - was later found alive in Cardiff Bay.
It is believed the child's mother is of Romanian origin while the other two arrested are understood to be a couple from Spain.
DNA tests are now being carried out to determine who the child's father is.
A Spanish police spokesman added the investigation remained open and they have not ruled out further arrests.