Birmingham managing director Brady arrested
Brady, who was also arrested last April along with the Championship club's co-owner David Sullivan as part of the same investigation, was questioned at a London police station and then released on bail.
"A 39-year-old woman was today arrested on suspicion of a further offence as part of the ongoing football investigation," a City of London police spokeswoman said.
She said it would be "inappropriate to give any further details at this stage".
Seven people have been arrested at various stages during the investigation. None has been charged.
They include former Portsmouth manager Harry Redknapp, now with Premier League Tottenham Hotspur, who was arrested in November 2007. He has always insisted that he has done nothing wrong.
Clubs investigated include Newcastle United and Scotland's Rangers.