Citibank parent Citigroup is understood to be under investigation by the financial regulator of the United States with regard to some potential breaches of securities law.
The issue revolves around the marketing and selling of what are called auction rate securities. These are a type of bond, most commonly used by municipal authorities when looking to generate funds and the question being looked into is whether the actual risks were understated by Citibank.
No comments have been forthcoming from Citibank so far regarding their discussions with the regulators. Instead they have a statement that says they have worked closely with all parties to make everything go smoothly.