It started as a system for taking children away from families deemed to be politically dangerous in the Franco era but then continued as an illicit business until at least the 1980s.
During the Franco regime, children of jailed left-wing opponents were stolen from their mothers with state approval and often the blessing of the Roman Catholic Church to purge Spain of Marxist influence.
However even after Franco was deposed, doctors, nurses, nuns and priests are all suspected of lying to mothers who were told their children had died during, or straight after, birth. Many of the real parents said they had been told that apparently healthy babies had died within hours of birth. They had never seen the bodies and the hospitals had taken care of the burials.
In a separate case, workers from an undertaker's in Malaga said they sometimes buried empty children's coffins that arrived from a local clinic.