European Commission (EC) regulators will launch an in-depth probe into a EUR300 million (US$467 million) bridging loan granted by Italy to cash-strapped national carrier Alitalia to address concerns it could constitute state aid.

The EC had remained tight-lipped on the issue - despite a string of reports suggesting it would decide to investigate - until this morning announcing the in-depth investigation.

"At this stage, the EC believes that the loan - which the Italian company has the option of - could constitute aid that is incompatible with the common market," it says in a statement. "The investigation will give all the interested parties the opportunity to submit their comments."

Italy granted the loan for Alitalia in April to shore up its financial position long enough to secure a fresh investor after the collapse of talks with Air France-KLM. Italy maintains the short-term loan - which is repayable with interest - is a commercial deal and consequently did not notify it as state aid.

The EC though sought further information from Italy on the loan and after reviewing this information has decided to open a full probe.

"As Alitalia has already benefited from rescue and restructuring aid, Italy cannot, in principle, grant it any more aid," the EC says.

"Launching this procedure should allow the EC to examine in detail the exact nature of this measure and the conditions under which the aid has been granted to Alitalia so as to determine whether it constitutes state aid. In this context, the EC will assess whether a private investor would have acted in the same way as the Italian Government."

The EC stresses the opening of the probe does not prejudge a final decision.