(see relates stories) Trani, February 1 - Prosecutors in the southern city of Trani have placed dozens of people under investigation on suspicion of usury and fraud in relation to derivatives operations at five major Italian banks including the troubled Monte dei Paschi di Siena (MPS). The probe, opened several months ago, also reportedly involves BNL, Unicredit, Intesa San Paolo and Credem. Prosecutors are investigating bank officials and managers believed to have traded in junk bond derivatives resulting in significant losses to investors. Some foreing money market traders are also under investigation. They are also trying to identify the representatives of the two main supervisory bodies, the Bank of Italy and stock-market regulator Consob, responsible for ensuring the genuineness of the derivatives deals. They could now face charges of lack of proper oversight. MPS came under public scrutiny last week following revelations of previously undisclosed losses of 720 million euros as a result of at least two shady derivatives deals. The scandal triggered a rush of criminal investigations and a political storm over the alleged interference of political parties in the banking sector. The centre-left Democratic Party (Pd) has a big presence in the foundation that controls MPS, headquartered in its historical stronghold of Siena.