European Union finance officials are stepping up efforts to sniff out suspicious insider trading before the attacks on the US.
German central bank president Mr Ernst Welteke says an examination by market regulators in his country has found unusual movements.
He says these involved not only in stocks from heavily affected industries, such as airlines and insurance companies, but also gold and oil markets.
"If you look at movements in markets before and after the attack, it makes your brow furrow," Mr Welteke says.
Belgian finance minister Mr Didier Reynders, who chaired an informal EU meeting of finance ministers in the Belgian town of Liege, says investigations into suspicious trading are also under way in Belgium, France and other countries.
Mr Reynders says ministers have ordered supervisory agencies in all 15 EU countries to work together to prepare a joint report on the results of their investigations by October 16th.
The first finance ministers' meeting since the attacks, intended to focus on preparations for the introduction of euro notes and coins next year, was instead dominated by the fall-out from the crisis.
Ministers agreed on a formula for government guarantees to keep their airlines flying after insurance companies cancelled war and terrorism insurance policies following the suicide hijackings.
German finance minister Mr Hans Eichel said the ministers had agreed on a "common position" to serve as insurer of last resort for Europe's flag-carriers, many of which had warned their fleets would be grounded as of midnight on Monday due to lack of sufficient insurance.
The measures would be short-term and limited to war and terrorism liability, he said, adding that they hoped to give airlines and insurance companies time to work out a solution on their own.