A scandal that has already cost Siemens 1.6 billion euros looks set to rumble on.

The US Securities and Exchange Commission and Siemens are investigating whether some Siemens' employees paid 100s of millions of euros in bribes to win telecommunications and other contracts, says Reuters.

Already the case has led to the resignation of chief executive Peter Loescher's predecessor, Klaus Kleinfeld, and chairman Heinrich von Pierer, although neither had been accused of wrongdoing.

To speed up the investigation, Siemens has offered an amnesty to staff to get them to come forward.

It says that so far 66 employees had come forward.

It adds that, as a result, 54 cases were under review, two applications for amnesty had been rejected and 10 granted.

The amnesty has now been extended until the end of this month to encourage more whistleblowers.