Autopsy results allegedly showed the group all died as a result of ingesting a toxic substance.
A baby, Samaira Kumar, was found crying by the roadside close to where the bodies were discovered.
It is believed she had turned one just a day before the family perished, news.com.au reported.
She was rescued by a young woman who stumbled across the grisly scene.
Neighbours of the family, who lived in the Nadi suburb of Legalega, said they had not seen them since the Saturday before— meaning the defenceless infant may have braved at least 36 hours alone in the wilderness, news.com.au has reported.
Mother-of-two Kelera Toloi, 25, said she stumbled across tiny Sumaira crawling near a cliff at Celekuta, a popular but rugged sightseeing spot.
Toloi said she did not know how the infant had managed to survive alone without shelter or sustenance but said her inability to walk had probably saved her life.
"I grabbed her and changed her soggy diaper straight away and fed her two milk bottles," she previously told The Fiji Sun.
"By the looks of it she was hungry but I wonder what inhumane mind could have done such a thing. Fortunately she did not walk or she would have fallen off the cliff.
"As a mother, it's a really sad scene."
