The details around the investigation of UBS by the Swiss bourse remain sketchy. Reuters reports that the investigation is into "whether UBS may have violated rules on releasing news last year when it announced a major restructuring and a settlement of Libor-related claims."
UBS says there is "no basis" for the investigation.
It's possible to piece together some details about what may be the subject of the investigation. And it seems that it may stem from leaks to a financial journalist.