All 10,000 tonnes of aluminium dross by-product stored in Mataura's old paper mill has been removed.
The waste - a by-product of aluminium production at the Tiwai Point smelter - releases deadly ammonia gas if it gets wet.
The Southland town's old paper mill site is situated next to the Mataura River.
The dross is a form of metal-rich scum off the top of aluminium processing pods, that is processed to remove the metal into a product that can then be converted into other materials, including ouvea premix which itself is a hazardous substance.
Environment Minister David Parker said the last bags of dross were moved from Mataura last Wednesday.
They are being stored in watertight shipping containers at the Tiwai Point smelter.
Parker welcomed the news saying it meant residents no longer needed to worry.
"Now that the Mataura site has been cleaned up, the focus will move to the removal of material from other known sites in Southland."
Mining company Rio Tinto has agreed to pay the $6 million clean up bill.