The 11-month-old seal pups' bodies were found by a tourism operator at Scenery Nook, on the south side of Banks Peninsula, in December.
The Department of Conservation (Doc) at the time said it appeared the seals were killed elsewhere before potentially being dumped from a boat and left to be found by visitors.
Three of the seals were buried by Doc rangers, while the other three were sent to Massey University for a necropsy.
Department of Conversation Mahaanui operations manager Andy Thompson said a post-mortem on three of the six pups showed that people were not to blame for the deaths.
Mr Thompson said it was possible a leopard seal, a sea lion or other fur seals could have killed the pups.
Fur seals, or kekeno, are protected under the Marine Mammals Protection Act and it is a criminal offence to harass, disturb or harm them.
