A parcel containing the body of a newborn girl was sent to a 59-year-old woman in South Jeolla province, South Korea.
A note inside the parcel said: "Please take good care of this package. Let the baby girl rest in peace."
China Press, quoting South Korean media, said police arrested a 35-year-old woman, who is the baby's mother and the daughter of the recipient.
Investigations are being carried out to verify if the baby was stillborn.
The arrest on Thursday came about after police found out that the parcel was sent from a post office in Seoul.
Closed-circuit television camera footage revealed that the sender was the recipient's daughter who ran away from home five years ago.