The Department of Conservation's keeping an open mind over the cause of deaths of around 25 fur seals discovered at Te Oka Bay near Christchurch.

DOC rangers are conducting a scene examination.

A couple were walking in the area last night when they made the discovery, and alerted the Ministry for Primary Industries.

DOC Operations Manager Andy Thompson says it's not the first time this year that something like this has happened in the area.

He says there have been several cases of seals dying in the southern bays of Banks Peninsula, but in those instances the seals were a bit younger than the ones found yesterday.

Several seals will be sent to a lab at Massey University in Palmerston North for a necropsy.