The controversial high-speed rail project to link Lyon in France to Turin in Italy faces investigation from the European Anti-Fraud Office.
Costs have rocketed and alleged mafia involvement on the Italian side is a cause for concern.
The EU has already contributed €450m and the probe will examine whether any fraudulent activity has taken place and if any EU money is involved.
One area expected to come under the microscope is the budget busting purchases of IT equipment by the Italians.
