The US Commodities Futures Trading Commission (CFTC) has subpoenaed US-based investment bank Goldman Sachs as part of an investigation surrounding inflated metals prices.
The commodities market regulator has demanded all documents and communications of a metals warehouse firm connected to the London Metal Exchange dating back to 2010, in a move that turns up the heat on Goldman.
The CFTC is looking into claims that the warehouses intentionally increased buyer costs by slowing the movement of supply.
In recent years a few of the big banks, including J.P Morgan and large commodities trading houses such as Glencore have increased their control over warehouse firms.
The Federal Reserve is also currently reviewing Morgan Stanley's behaviour in commodities markets.