Britain's financial watchdog said an investigation into share trades before attacks in the United States has so far found no evidence the perpetrators profited from their inside knowledge.
But chairman of Britain’s Financial Services Authority Mr Howard Davies said the investigation into some unusually large stock trades before the September 11th attacks was far from over.
An international investigation into share trading has focused on short selling of insurance and airline stocks, which fell heavily after the terrorist attacks in New York, Washington, and Pennsylvania.
There are also suspicions the attackers may have invested in oil and gold, which rallied as investors sought safety in a crisis.
"London share volumes in the week or so before September 11th were high, but not uncommonly so, and many transactions were readily explained and perfectly acceptable," Mr Davies said.
"The specific trails we have already followed have not led us to any discovery of improper activity. However, we have quite a way to go," he said.
Earlier he told a news conference there were instances where individual stocks were traded in "unusually sizeable amounts".
"This may have been because funds were positioning themselves ahead of an economic downturn. But we are following up these cases," he said.