A 250 tonne piece of the Rena has ripped off the wreck and fallen to the sea bed.
Vital salvage equipment has also been lost overboard.
Maritime New Zealand said this week's high wind and rough seas caused a large piece of the fore-section to rip free from the aft portside of the wreck.
The piece that came off the ship was about 25m long and weighed about 250 tonnes.
The section included the boat landing platform and access ladder, with gas cutting equipment also going overboard.
No salvors were on board at the time and the loss of equipment has not delayed salvage efforts.
Francis Leckey, senior salvage master of the Florida-based salvage company Resolve Salvage & Fire, inspected the wreck.
"While on board, the wreck was still rolling and pitching," he said.
Meanwhile, salvors are continuing to work onboard.
In their bid to reduce the wreck to below the water-line, salvors removed about 45-50m pieces of steel this week.
These pieces, which weighed about 100 tonnes, were removed from the forecastle, aft portside and transverses.
The Braemar Howells/Unimar team is continuing to work on debris recovery, using the newly arrived Tasman Challenger - a 30m vessel fitted with a crane.
This week, the team spent time putting down moorings in preparation for work that will occur on the seabed around the Rena.
The wreck was hooked onto the mooring yesterday, so baskets could be dropped down and loaded with debris by divers.
Braemer Howell's operations manager Mike Richards said while the weekend's weather forecast was unlikely to be favourable, the at-sea operations were set to continue as soon as conditions eased.
Shoreline debris retrieval has continued at Matakana Island and Coromandel beaches, where plastic beads and small amounts of flotsam, such as noodles and container foam have been collected.
The clean-ups have been focused on the northern tip of Matakana and around the Tairua area in the Coromandel.