With very low interest rates, market players can sell forward aluminium at a higher price than the costs involved in keeping it in a warehouse.
While premiums for aluminium appear to be stabilising, the warehousing situation has not fundamentally changed, despite a general flattening of the aluminium forward curve.
"Certainly the warehousing phenomenon still has some way to go before it ends," Deutsche Bank said.
Aluminium last traded on the London Metals Exchange at US$1871, down 9.7 per cent from last year's closing level of US$2073 a tonne.
The bank estimates that Chinese producers are significantly cash negative at the current price, and several Western producers will be struggling as well. There had also been a lack of demand strength from the global marketplace.
Tiwai is 80 per cent owned by Pacific Aluminium, the subsidiary of Rio Tinto the Anglo-Australian mining giant has up for sale.