Salvage teams working on the Rena are removing shipping containers of wood from the bow of the wreck.
Maritime New Zealand says emptying the containers and preparing bundles of timber for removal by helicopter is labour-intensive.
The Rena ran aground on the Astrobale Reef off the Bay of Plenty coast on 5 October and broke up last month.
Maritime New Zealand says 70 containers of the estimated 150 that fell off the ship, have now been recovered from the sea and beaches. In total, 549 containers are now ashore.