AIB has ceased all foreign exchange trading operations in Allfirst while the investigation gets under way.

The bank has suspended five employees including the executive vice president and head of treasury, the senior vice president in charge of treasury funds management, the senior vice president with responsibility for investment operations and two other staff.

Mr Pat Ryan, head of AIB's treasury operations in Ireland, has gone to Baltimore to take day- to-day responsibility for the running of that business. Mr Michael Cullen, an executive from the operations side of AIB's treasury division has also travelled to Allfirst to assist Mr Ryan.

Chief executive Mr Michael Buckley said the suspensions were being made to comply with best practice where those immediately associated with the area of fraud stand aside to allow an investigation.

"The fact that anyone is suspended is not an implication of guilt. They are helping with the investigation," he said yesterday.

According to AIB, Allfirst's treasury business was run independently from AIB group. The head of treasury reported to Allfirst's chief executive, Ms Susan Keating, who in turn reported to chairman Mr Frank Bramble.

Mr Rusnak had worked at Allfirst for seven years as a foreign exchange trader. He typically executed an average of 60 to 100 transactions every day.

Mr Rusnak had been under investigation for several weeks, but failed to report for work on Monday.

At that stage, AIB reported the matter to the US Federal Bureau of Investigation and sought its assistance.