How the $750m was lost

Trader entered into large number of foreign exchange deals He appeared to have offset risk with 'options' deals Original deals proved bad, causing big losses Options deals proved 'fictitious', providing no protection against the losses Click here for full details

But emerging from the session, chief executive Michael Buckley merely restated his regret at the failure of security controls, and pledged to discover the truth behind the loss.

And bank chairman Lochlann Quinn, pressed on who was to blame, said: "I want all the facts, not some of them."

Earlier, lawyers for John Rusnak, the trader at the centre of the scandal, reaffirmed that he had voluntarily met FBI officials and denied theft.

Mr Rusnak, who was earlier thought to have been on the run, had in fact been with his family and in talks with federal authorities in Baltimore, his lawyer Bruce Lamdin said.

"My client is not a fugitive," Mr Lamdin said, adding that the loss of the cash was "not a theft case".

Ireland's central bank has also revealed it is to send a delegation to the US to investigate the furore at a firm which had ranked as the country's largest commercial bank.

Leeson's shock

Although the losses at AIB's US subsidiary, Allfirst, have sparked comparisons with the collapse of Barings, the Irish bank has been at pains to point out that the blow it has taken, while heavy, will not be fatal.

The bank said it would still report a profit for 2001, despite writing off the $750m.

I find it exceptionally frightening because I know how basic the checks were that should have been done to catch me

Nick Leeson

In 1995, Singapore-based derivatives trader Nick Leeson caused the collapse of the British bank Barings by running up £830m ($1.17bn) in losses on unauthorised derivatives trades.

On Thursday, Mr Leeson told the BBC he was shocked that the Allfirst fraud hadn't been spotted.

"I find it exceptionally frightening because I know how basic the checks were that should have been done to catch me," he said.

"It is not a great advertisement either for the bank or the banking industry as a whole."

Theft denied

Mr Rusnak's lawyers denied allegations that the 37-year-old churchgoing father of two had stolen any money from his employers.

David Irwin, also representing Mr Rusnak, said: "If they're claiming that he stole money, that won't pan out. I'd be surprised if they ever came up with evidence that he stole money".

What the bank doesn't know

Full sequence of events Whether others were involved Whether any individuals profited or it was just a 'right royal mess' Why internal controls failed to spot the fraud

The comments came after AIB said it had called in the FBI to investigate what the bank described as "a complex and very determined fraud".

Allfirst alerted the FBI after Mr Rusnak, who had been helping with an internal enquiry into the trading losses, failed to report for work on Monday.

The FBI has not issued a warrant for Mr Rusnak or filed any charges.

'Right royal mess'

AIB's probe is focusing on how losses on foreign currency transactions were disguised with fictitious options trades.

In comments on Wednesday, AIB said Mr Rusnak had artificially entered a "very, very large number" of unauthorised transactions to offset losses he was making on real trades.

John Rusnak

Age: 37 Wage: approx $85,000 Home: Baltimore, Maryland Married with two children Regular churchgoer

It said it did not yet know whether the losses were intended to be for the financial benefit of Mr Rusnak or others, or whether it was just "a right royal mess".

But it said initial signs were that internal and external collusion were involved.

The losses were uncovered during a management review of the treasury division of Allfirst and are thought to have occurred over a 12-month period.

AIB on Thursday confirmed that the deals concerned dollar-yen trading.