A bacterial infection may have caused the die-off of pipi beds in Northland's Ngunguru estuary last autumn.
Scientists who tested the rotting pipis have found what is known as a Rickettsia-like bacteria, which has been seen before in shellfish, though it has never been known to cause mass deaths.
Northland Regional Council environment committee chair Joe Carr said the pipis could have succumbed because they were already under some other environmental stress.
