UBS AG could be set to record significant losses in the third quarter of 2011 as a result, and, following the announcement, the institute's shares tumbled as much as 9.6 per cent in Swiss trading.
According to UBS, a rogue trader was accountable for the loss - but no client positions have been affected as a result.
In a statement made prior to the opening of the stock market, the bank explained: "The matter is still being investigated, but UBS's current estimate of the loss on the trades is in the range of $2 billion."
Beyond this assertion, however, spokeswoman at the lender Tatiani Togni declined to add any further comment.
Earlier in the year, UBS recorded a net profit of $1.89 billion for the second quarter of 2011, with its investment bank posting pre-tax revenue that was ten per cent greater than the first quarter.
By Tony Aynsley