Banks are reducing their investments in physical commodities amid investigations by the US Congress and regulators into whether involvement in the markets poses a risk to the financial system. The Senate panel's report last month alleged that Goldman Sachs moved aluminium from warehouse to warehouse to influence how much customers paid for storage and financial products tied to the metal.

Jacques Gabillon, head of Goldman Sachs's global commodities principal investments group, said at a Senate hearing at the time that the firm had received interest in Metro from potential buyers in Europe, Russia and China. He disputed the senators' claims of market manipulation.

The US Federal Reserve has been examining whether it's appropriate for financial companies to own commodities and trade derivatives linked to them at the same time.

JPMorgan Chase sold some commodities businesses to Mercuria Energy, a trading firm. Morgan Stanley's deal to sell its oil-merchanting business to OAO Rosneft failed to win regulatory approval, the state-controlled Russian oil producer said on its website on Monday.

The billionaire Reuben brothers, Simon and David, have amassed a fortune investing in property and Russia's aluminium industry.

Aluminium users such as beer brewer MillerCoors last year complained that warehouse operators authorised by the London Metal Exchange were inflating costs by constraining supply.

Goldman Sachs's Metro unit paid "millions of dollars in incentives" for firms to move metal between its sheds, leading to longer queues for other users waiting to remove metal and boosting rental fees, according to the Senate report.