Image copyright Fiji Police Media Image caption Police at the site where five bodies were found in he Nausori Highlands, western Fiji

A young mother found a crying baby close to five of the child's dead family members in Fiji's Nausori Highlands, local media reports said.

Kelera Toloi, 25, was among passersby who rescued the one-year-old from the roadside on Monday.

Locals spotted the baby crawling close to where five bodies were discovered at the bottom of a cliff.

Investigators were questioning two people, reportedly a man and his wife, over the deaths.

A post-mortem revealed that the family died after ingesting "an alleged harmful substance", Fiji police said.

The baby, named by local media as Samaira Kumar, is said to be safe after she was taken to hospital.

"By the looks of it, she was hungry but I wonder what inhumane mind could have done such a thing," Ms Toloi told the Fiji Sun. "Fortunately she did not walk or she would have fallen off the cliff."

The family members have been named by local media as carpenter Nirmal Kumar, 63, his 54-year-old wife Usha Devi, their 34-year-old daughter, Nileshni Kajal and her two daughters Sana, 11, and Samara, eight.

Mr Kumar's brother, Raj Kumar, told Stuff NZ that the family was struggling to come to terms with their deaths.

"It's not one, it's five. We are trying to do as best as we can and it's not an easy time," he said.

Mr Kumar said relatives from New Zealand, Australia and Canada were flying to Fiji for the family's funeral on Saturday.

The Kumars, who lived in Legalega in the city of Nadi, left home on 24 August and did not return, neighbours said. In a statement on social media, Fiji police said investigators were interviewing a person of interest, a man who was known to the family.

A second person, reportedly the wife of the man, was also taken in for questioning. Both were released without charge after 48 hours in custody, local media reported. They are said to be residents of Christchurch, New Zealand.

A court dismissed an application to detain and question the first person of interest for longer, FBC News reported.

Further tests were being carried out on the substance believed to have resulted in the deaths of the family, police said.