They hope to get defectors, or captured documents, and people who might describe more about what al-Qaeda actually is

David Johnson, New York Times

"What we do know is the people involved in this were trained in Afghanistan, they used various locations in western Europe to plan the attack, and then they came to the US to carry it out."

Ms Tucker said every day investigators were gaining a better idea how much support the hijackers received in the United States

"I think one thing we've realised is that there weren't a lot of other people that may have been directly involved. They used a lot of people for support, but those people may or may not have known what they were involved in," she said.

"For instance, there's a group of people in Virginia that assisted several people in getting false identification, false United States identification.

"We know there are a couple of instances of that - but how directly involved other people were is still something that we're looking at, but we're not finding extensive information on," she added.

Overseas connection

According to the New York Times' David Johnson, who has been following the investigation from day one, the authorities have largely finished their inquiries in the US, and are now looking overseas.

"In Germany principally, the FBI's trying to understand the kind of intellectual origins of the plot - who was behind it," he said.

America's most-wanted are posted on the FBI's website

"They are trying to understand the financial background of this, primarily in the United Arab Emirates, and in Afghanistan. They hope to get defectors, or captured documents, and people who might describe more about what al-Qaeda actually is and how it operates," he said.

Much of the work on the money side is being done within the cavernous corridors of the US treasury.

Spokeswoman Tasia Scolinos said some $60m of assets have already been frozen, but was less sure about what is still out there.

"That's probably a question that is ongoing, both here at the Treasury Department, and also at the FBI and other aspects of the US Government, trying to figure out that figure," she said.

FBI 'sidelined'

The FBI, famously described by one critic as fat, dumb and happy in the days before 11 September, it is now busily and successfully repairing its image here.

President Bush is discussing new tactics with his advisers

But former US counter-terrorism official, James Lewis, said with the government intending to kill people not prosecute them, the agency has almost been sidelined.

"The FBI's role has declined a bit because this administration has decided to take more of a military or intelligence approach, he said.

"You just want the evidence to let you be sure you're hitting the right target, rather than the kind of law-enforcement judicial approach, where you need enough evidence to stand up in court," he added.

It is clear that the emphasis here has now switched from investigating the 11 September attacks, to eliminating those responsible abroad and preventing further acts of terrorism at home.