Foul play has been ruled out in the deaths of about 40 fur seals found in Banks Peninsula at the weekend, but scientists still don't know how they died.

Photo: 123rf

A ranger counted 41 dead New Zealand fur seals, or kekeno, at Te Oka Bay and sent six of them to Massey University for post-mortem examination.

DOC Mahaanui (Christchurch) operations manager Andy Thompson said it was possible the pups died in a colony nearby and washed up at Te Oka Bay in the large swells from a series of storms.

Staff think the seals had been there since early July.