Authorities trying to unravel allegations of Libor rate rigging centred on former trader Tom Hayes have written to 22 individuals to tell them they are under investigation, a court has heard.
The Serious Fraud Office contacted the individuals last month after Hayes was arrested last year to tell them the part they may have played in the alleged conspiracy was being scrutinised.
None has been charged and many have not been interviewed, London's Southwark Crown Court heard.
Hayes, 34, a former UBS and Citigroup trader, of Woldingham, Surrey, appeared alongside Terry Farr, 42, of Great Wakering, Essex, and James Gilmour, 48, of Benfleet, Essex. They are not expected to face trial until 2015.
Hayes faces eight charges spanning the period from August 2006 to September 2010 which allege plans to defraud "with the intention that the economic interests of others would be prejudiced and/or to make personal gains for themselves or another".
The charges allege a conspiracy to defraud in dishonestly seeking to manipulate yen libor rates, said to include a number of employees from a number of City financial institutions.
Libor is the term for benchmark rates that underpin hundreds of trillions of dollars of contracts from mortgages to corporate lending.
Gilmour has been charged with one count of conspiracy to defraud, between August 2006 and December 2009.
Farr faces two counts of the same offence, one alleged between August 2006 and December 2009, and a second between December 2009 and September 2010.
Mr Justice Cooke lifted reporting restrictions when all three men appeared in court. No pleas were entered and a further hearing will take place on a date to be fixed later this year.
Much of the hearing was taken up with legal argument over an injunction over identifying the 22 after a draft version of the indictment against Hayes was drawn up which included their names.
The judge lifted the injunction against the Wall Street Journal, that was put in place last week, but agreed to remove the men's names from the indictment.
Mukul Chawla QC, for the SFO, said of the 22 individuals: "Of those that are named, some have been informed that the Serious Fraud Office would like to interview them.
"But a large number have not been interviewed or for that matter previously been put on notice that they are within the radar of the Serious Fraud Office."
Later, the judge agreed to extend legal aid for defendants in the current case to allow them each to be represented by a junior barrister led by a QC.
He said: "It seems to me an entirely appropriate case where there should be leading counsel and a junior."