Six metre swells overnight caused the stern and forward section of the stricken cargo ship Rena to move, spilling containers into the rough seas and creating a moving debris field.
Maritime New Zealand (MNZ) said observation flights showed containers and debris had fallen from the ship as it was hammered by massive swells last night.
Response and recovery manager David Billington said two containers had been spotted floating about two kilometres from the wreck.
Bags of milk powder and timber were also floating in a debris field spreading about two nautical miles south east of the vessel, he said.
He advised boaties to avoid the area between the Rena and Motiti Island.