Police are threatening to prosecute anyone caught taking goods from containers that spilled off the grounded cargo ship Rena.
Aerial footage from a ONE News chopper shows a number of containers floating in the water. One appears to have been split open with blue smoke coming off in a possible chemical reaction.
Western Bay of Plenty police inspector Karl Wright-St Clair said the containers remained the property of the ship owners.
He said people have a statutory responsibility to notify authorities about their location.
Anyone caught interfering with the containers would be dealt with by police.
"I can't reiterate enough, please do not attempt to open any of the containers," Wright-St Clair said.
"Not only do they remain the property of the original owners or insurers, they may contain hazardous material and need to be dealt with carefully and appropriately."
Maritime New Zealand (MNZ) now believes 30 containers have fallen off the stricken cargo vessel as heavy weather forced it on to a 19-degree starboard lean . It was earlier thought 70 containers had fallen form the ship.
The containers fell off the back of the vessel and more are likely to follow, Ross Henderson from Maritime New Zealand (MNZ) told TV ONE's Breakfast.
"They are semi-submerged so they are a real hazard for mariners," he said.
"Some of these containers could come ashore.
"It's important to realise the material in the containers remains the property of the owners."
There were around 1300 containers onboard the Rena. The ones that fell off this morning are thought to be empty.
Others contain a variety of cargo ranging household items and bottles of wine, to 11 containers which contain potentially dangerous chemicals.
There are four which contain Ferrosilicon, an alloy which produces hydrogen on contact with water and could pose an explosive risk.
"At last report those materials were wrapped and intact within the containers, but once containers start floating and bobbing around it is possible it could become a hazard," Henderson said.
Environment Minister Nick Smith told TV ONE's Breakfast the containers with the dangerous materials were further down the vessel and he would be surprised if they had come loose at this stage.
"The number of hazardous goods on this vessel is less than on many vessels," he said.
"The 1700 tonnes of heavy oil is the real environmental danger."
Salvage experts have been trying to work out how to get them off but the weather is hindering their efforts.
Bruce Anderson from MNZ says recovery boats are starting to corral those containers.
Anderson is warning the public not to get nosy as the containers may contain hazardous materials or rotting food.
"If your rubbish bin is sitting there for a week without any cooling it tends to get very hot and smelly and you don't want to be opening those sort of containers on a beachline."
Brian Kiddie from the NZ Federation of Commercial Fishermen said the containers may be dangerous for boaties.
"You hit one of those it means damage a steel boat might be alright but a timber boat may sink it."
In 2007, beaches along the Devon coast were left strewn with thousands of items like makeup, video recorders and more than a dozen BMW motorcycles after container ship MSC Napoli ran aground.
Thousands of looters turned up to claim the washed up cargo, which under British law, they could keep if the owner didn't want it back.