Environmental officers are on board the Rena assessing noxious fumes from the rotting food on board.
Maritime New Zealand salvage unit manager Bruce Anderson said the first priority was ensuring the ship was as safe as possible for salvage teams.
The cargo ship grounded on the Astrolabe Reef near Tauranga a month ago with 121 containers holding perishable food goods, which have been decomposing.
Salvors are also back on board today, taking advantage of improved weather conditions.
Mr Anderson said they were continuing to transfer oil and lubricants to a centralised tank, which would make it easier to pump on to the Awanuia.
Dive teams hoped to continue assessing damage to the hull of the stricken ship.
There would be a further update late this afternoon.
Meanwhile, the Bay of Plenty Regional Council is developing a long-term plan for monitoring the environmental effects caused by the ship's grounding.
The plan - a partnership between local government authorities, central government agencies and iwi - will cover areas known to have been affected by oil and container debris.
According to the regional council's science manager Rob Donald the monitoring could continue for several years.
"We will not be aware for some time of the full impact upon the Bay of Plenty coastline of the Rena grounding,'' he said.
"Monitoring will be our best way to understand the impact on our beaches and marine life. In the first instance we want to be able to give health authorities the information they need to advise the public on the safe recreational use of beach areas and the safety of seafood.''
Mr Donald said the environmental monitoring that began after the Rena stranding on October 5 involved baseline sampling of water, sediment and seafood. That was before the oil spills affected the coastline and offshore islands.
"These samples are being analysed and the results will be compared to samples that are known to have come into contact with the oil,'' he said.
