The FBI has said it is conducting a fraud and embezzlement investigation into the circumstances surrounding the loss of $750 million (€864 million) at AIB's Allfirst Bank in Baltimore, writes Conor O'Clery, International Business Editor

However, the FBI has not yet issued a warrant for Mr John Rusnak, the currency dealer who AIB says is at the centre of the fraud, according to Mr Peter Gulotta, special agent for the FBI's office in Baltimore.

Officials at Allfirst are rushing to complete their part of the investigation, which AIB says is complex. AIB's board in Dublin has ordered a full report on the matter within 30 days.

The Allfirst executives are preparing documents to provide to the FBI as evidence that Mr Rusnak created phoney trades during the last year.

This process involves getting banks in Asia to certify that options recorded as trades with them by Mr Rusnak do not exist.

Bank officials are also keen to have their internal investigations concluded as quickly as possible to satisfy regulatory bodies like the Securities and Exchange Commission and the Federal Bank of Richmond that the loss was the once-off action of a rogue trader, and that full disclosure has been made.

Three of the banks top treasury officials suspended over the affair are cooperating fully with the investigation, an Allfirst official said.

Mr Rusnak met the FBI in Baltimore, according to a lawyer, Mr Bruce Lamdin. Accompanied by another lawyer, David Irwin, Mr Rusnak went to the US Attorney's office in the city where the FBI sat in on the interview.

On Tuesday, Allfirst reported to the FBI that Mr Rusnak was missing, having failed to contact him since Sunday evening, but Mr Lamdin denied that Mr Rusnak had gone on the run. "He's been home with his family, quite frankly," he said.

The FBI came looking for Mr Rusnak at his Smith Avenue home in Baltimore's north-west suburbs on Tuesday evening, according to neighbours, and later an FBI official told a local resident that they had contacted Mr Rusnak "out of state".

Earlier yesterday, Mr Irwin said the trader did not steal from Allfirst."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," he said.

Mr Irwin said Mr Rusnak was not a fugitive, "he is not going anywhere."

He added: "One thing is becoming clear, Mr Rusnak is not a thief. There will not be, as reported, $750 million found missing at Allfirst. "

More details have been emerging about Mr Rusnak, who was one of just two foreign exchange dealers operating at Allfirst.

Two weeks ago he began requesting unusually large amounts of money for his trades and the first seeds of suspicion were sown in the mind of one member of the Treasuries section responsible for verifying trades in currencies, equities and other bank business. This unit works from a different floor from the traders to maintain a separate oversight.

This bank official became concerned that Mr Rusnak was resisting oversight and complaining that with the limits imposed he could not trade effectively.

Meanwhile, credit rating agency Fitch said the scale of the suspected fraud cast doubt on management and supervision at the AIB-owned bank, while Standard & Poor's said it was considering a downgrade. However Moodies said it would leave Allied Irish Bank's rating untouched because it "expects the impact of this event to be contained and not have broader implications for the group" .