UBS said it estimated it had lost $2 billion from unauthorized trading, by one trader. In connection with the case, London Police arrested a 31-year-old man, in the middle of the night.

On its corporate web site, the Swiss financial firm, whose U.S. operations feature a large trading floor in Stamford, said:   "UBS has discovered a loss due to unauthorized trading by a trader in its Investment Bank. The matter is still being investigated, but UBS's current estimate of the loss on the trades is in the range of USD 2 billion. It is possible that this could lead UBS to report a loss for the third quarter of 2011. No client positions were affected."

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