Brussels - The European Union's executive on Friday launched a probe into a plan to rebuild fallen Belgian banking giant Dexia, which in September received a multi-billion-dollar bail-out from the Belgian, French and Luxembourg governments.

"We cannot reach a favourable conclusion at this stage on the plans submitted to us. We therefore have to study them in depth," EU Competition Commissioner Neelie Kroes said in a statement.

If the probe decides that the plan breaks EU rules, the European Commission could order Dexia to draw up a new, tougher restructuring scheme or pay the money back.

Dexia was one of the first European banks to suffer from the global financial crisis. In September, Belgium, France and Luxembourg decided to keep it afloat with a cash injection of 6.4 billion euros (8.2 billion dollars) and a 150-billion-euro guarantee.

In November the commission, which oversees the EU's strict laws on competition, ruled that that aid was legal as long as it was accompanied by a restructuring package designed to make sure that Dexia could survive without further handouts.

But the commission "has doubts about the viability of the proposed business model, whether Dexia's own contribution to its restructuring costs is sufficient and about compensatory measures to eliminate distortions of competition," the statement said.

The fact that the commission has opened an investigation does not mean that Dexia's rescue was necessarily illegal, officials stressed. (dpa)