One of the false accounting charges against Mr. Adoboli dates to October 2008 — at the height of the financial crisis and less than two years after he became a trader for UBS. The charge that Mr. Adoboli's rogue trading had been going on for years raises embarrassing questions about the bank's controls and oversight. After writing down more than $50 billion on bad subprime mortgage investments, the chief executive of UBS, Oswald J. Grübel, had pledged to improve the bank's risk management when he took over in 2009.
The Financial Services Authority, Britain's equivalent of the Securities and Exchange Commission, and Swiss market regulators said on Friday that they would begin an independent investigation into the bank's "control failures."
With the charges going back to 2008, "it would seem there was a systematic pattern of trading," said Lindsay Thomas, managing director at Sustainable Risks, a risk management consulting firm, and a former director at the F.S.A.
Before he landed a job on the bank's trading desk, Mr. Adoboli had worked in its back-office support. UBS executives suspect that his knowledge of the bank's computer systems and protocols enabled him to override the internal controls that would have caught his trading, a person close to the bank said.
Representatives for UBS declined to comment.
This weekend, UBS managers are continuing to comb through dozens of trades made by Mr. Adoboli. The transactions under the microscope, according to a person briefed on the situation, typically began as client trades, packaged for either a hedge fund or for another arm of the bank.
