Local media reporting that a Kiwi man was spoken to by police after family found dead in the highlands.

An investigation is under way into the deaths of five people in Fiji and local media have reported that a New Zealand man has been questioned by police.

Five people were found dead in Nadi, Fiji, on Monday. The post-mortem examination results showed they died as result of ingesting a toxic substance.

FBC News - which is government-owned - has reported that police have spoken to a man from New Zealand.

READ MORE: Fiji deaths caused by ingestion of toxic substance, post-mortem examination results show

A second person believed to be related to the man has also been spoken to, FBC News reported.

On Monday, the bodies of a 63-year-old carpenter, Nirmal Kumar, his 54-year-old wife Usha Devi, their 34-year-old daughter, Nileshni Kajal and her two daughters aged Sana, 11, and Samara, 8 were found at the Nausori Highlands.

A crying one-year-old, Samaira Kumar, was found crawling by the roadside close to where the bodies were found.

Samaira is believed to be Nileshni Kajal's niece. The child is in hospital, the site reported.

Post-mortem results found all five people died after ingesting a substance, however, police have not yet revealed what that substance is.

FBC News reported, that on Thursday, the Lautoka Court dismissed an application made by the state for police to hold a person of interest for longer than 48 hours in relation to their investigation into the deaths.

No charges have been laid. The miscellaneous application was made for the man - which FBC News reported was from New Zealand - to be held further as police needed more time to question him.

But the defence counsel objected and the court dismissed the application, FBC News reported.

The family's neighbours in Legalega, Nadi have said the family had gone out on Saturday afternoon and did not return home. Family members also say that all their mobile phones were left at their home in Legalega.

In a statement to the "The Fijian Times", police spokesperson Ana Naisoro said more tests would be conducted by the Fiji Police Chemistry Scientific Lab in Nasova following the post mortem examination conducted on the five victims.

She said investigations into the deaths were continuing.