Within a day of the hijackings last week, the FBI asked SunTrust executives for information on roughly nine people who are under investigation. The bank turned over data from "several checking accounts." All of them were opened in Florida. A bank source says there weren't big accounts, "there was nothing unusual about the way they were opened or operated. Nothing caused any alarms to go off."
Now, the FBI is asking all banks to check their records for transactions by the suspects, and if they find anything to immediately contact the FBI.
Another important link in the investigation is the Federal Reserve, which operates America's wire transfer system. Most money from abroad comes into the U.S. via wire, and workers are now looking for any transfers involving the suspects. It's a huge job that can only be done overnight when the wire system isn't active.
And it doesn't stop there. Officials are clamping down globally on the intricate web of financing possibly used by terrorists and their supporters. Barclays Bank in London this week froze an account belonging to a man with suspected links to the attacks.
"We're going to go after individuals, individual accounts, and we're going to begin today to block accounts," said Treasury Secretary Paul O'Neill.
Meantime, the Securities and Exchange Commission is "aggressively" pursuing leads on unusual activity in the options market, in the days leading up to the attack.
As CBS News previously reported, there was an extraordinary number of trades or "puts" betting that American and United Airlines stock prices would plummet. Those "puts" turned millions in profits for whoever bet the stock would fall. The question is did those customers have advance notice of the tragedy that was about to happen.
One of the brokerage firms that placed a small number of those orders, TD Waterhouse, says it found no unusual activity in advance of the attack. Others firms are keeping publicly silent on the question.
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