Police believe the man is known to the Indo-Fijian family whose members died, with local media reports saying he is believed to be a natural healer.
Post mortem findings are consistent with the ingestion of a substance by all five victims leading to their deaths.
The Lautoka court yesterday dismissed a police application to keep the New Zealander in custody for longer than 48 hours without facing charges.
The FBC reports the man's wife was also questioned and released last night.
A stop departure order has reportedly been issued by Fiji authorities for the couple who live in Christchurch.
The five people whose bodies were found were 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 Sana, aged 11, and Samara, aged 8.
The five bodies were found in the Nausori Highlands on Monday along with a one year old found crawling at the scene who is now in hospital.
Fiji police are conducting more tests following the post mortems.
Meanwhile, New Zealand's Ministry for Foreign Affairs and Trade says it won't be providing consular assistance to the man in Fiji.
It says the High Commission in Suva is aware of a Fijian citizen in Suva assisting Fiji Police with their enquiries.
It says due to privacy considerations no further details will be provided.