The Samoa Observer newspaper reports local mayor, Fa'alogo Sasauli Moli, saying the council had been to every family in Lauli'i and concluded that someone must have dumped the baby.
Fa'alogo said all babies born in the last eight months in the village had been accounted for.
He said the village council will not stop until they uncover who did, what he called this "unchristian act".
Meanwhile the police have advised the public to refrain from posting pictures of the decomposing body on social media.
Deputy Commissioner Papalii Monalisa Keti said people sharing the disturbing photos are insensitive to others who are or experiencing the loss of loved ones, including a child.