The European Commission confirmed yesterday that it was investigating a complaint that the low-cost airline Ryanair has been receiving illegal state support for its operations at the airport of Pau in the south-west of France.

The investigation follows on from an inquiry into aid given to Ryanair by a regional government in Belgium to support flights in and out of Charleroi. On Tuesday, the Commission ruled some of that aid illegal and said the government should recover an estimated €3-€4 million.

But the Commission said its inquiries into the aid at Pau, reportedly at the level of €400,000 a year, were informal and had not been authorised as an official investigation by the college of commissioners.

"We received a complaint in the spring of last year. We wrote a letter to the French authorities, asking for information. The inquiries continue," said Mr Gilles Gantelet, spokesman for the European Transport Commissioner, Ms Loyola de Palacio.

He said the Commission was bound to investigate when it received a complaint.

He said the identity of the complainant had to remain confidential.

Mr Gantelet said the inquiry could be stepped up to the level of an official investigation or it could be dropped.

EU sources suggested yesterday the inquiries into the Pau complaint would not be completed within the next two months and might take even longer than six months.