Goldman Sachs last week bought US-based Metro International in a deal that rival bankers and warehouse executives valued at about $550m. The bank declined to comment on the amount but said: "The company will continue to operate independently, keeping its name and headquarters in Detroit and [it] will be run by the existing management team."

Last month JPMorgan acquired UK-based Henry Bath as part of a deal to buy a large chunk of the RBS Sempra Commodities business for $1.7bn.

Swiss-based oil and metals trader Trafigura this week said it had bought UK-based warehouse company NEMS Ltd for an undisclosed sum. Pierre Lorinet, Trafigura chief financial officer, said the acquisition reflected the trader's "commitment to ongoing investment in logistics and warehousing within the metals" sector. "NEMS will continue as an independent operation," he added.

The deals will leave Rotterdam-based C. Steinweg and Pacorini, based in Trieste in Italy, as the only two big independent warehouses. In addition, Singapore-based CWT Commodities is a medium-size operator in the sector, with a strong network in Asia.

Industry executives and bankers say Goldman Sachs and JPMorgan paid handsomely for their warehouses. "They are buying at the top of the market," one executive said, referring to the current mountain of metal being stockpiled.

But traders say the banks are likely to make substantial profits. With so much metal in depots, warehouses will earn rental fees for months. Fees are poised to rise by about 5 per cent on average in April, LME data suggests. Goldman Sach and JPMorgan will be paid a so-called "free-on-truck" fee when metal starts to move out of depots, increasing profits.

Chief users of warehouses services are mining companies and traders such as Glencore, Gerald Metals or Noble, and physical hedge funds such as Red Kite.

Eoin Treacy's view Warehousing and inventory management take on renewed importance in a commodity bull cycle. This is because if one relies exclusively on just-in-time sourcing of raw materials, the risk of paying higher prices than would have been the case if one simply took delivery and held the physical metal increase considerably. The fact that major investment banks are taking ownership of warehousing facilities indicates they have bullish long-term forecasts for volume and warehouse traffic. This might not be the only reason for such purchases.

Other than the fact that warehousing is a profitable business in a commodities boom there are additional benefits from the perspective of an institutional sell side organisation. Warehouses may act as a hedge on exposure to long metal positions because they tend to generate more fees when stockpiles are high, which sometimes coincide with commodity prices coming under pressure. .

There is also the potential to gain market intelligence from the warehousing business because they will have an additional insight into the businesses of their buy side customers.