Police said they had detained Rosario Porto, 44, and journalist Alfonso Basterra, 49, on suspicion of homicide after their daughter's body was found at 1:30 am Sunday in woodland near the northwestern city of Santiago de Compostela.
According to Spanish media reports, a couple heading to a nightclub discovered the body of the girl, Asunta Yong Fang Basterra Porto, just hours after she had been reported missing by her parents.
An autopsy and forensic tests were reportedly conducted before the girl's body was cremated on Tuesday.
The parents were shown on national television being led in handcuffs to their respective homes in the centre of Santiago de Compostela for the police searches.
Small crowds of onlookers gathered, some hurling insults at the suspects as they entered their apartment buildings in a case that has dominated newspaper headlines and television talk shows.
The mother, a Spanish citizen who acted as French honorary consul in the northwestern region of Galicia from 1996-2006, is due to be questioned by a judge on Friday, a court official said.
The judge will decide on her custodial status and any charges she faces, the official added.
No date has been released for the father's hearing.
Detectives were investigating the possibility that the girl stood to inherit money from Rosario Porto's parents, who died recently, a police spokesman said without giving further details.