The European Commission said Wednesday that it has launched an in-depth investigation into whether subsidies to France's La Rochelle airport have violated the aid rules of the European Union (EU).

The airport, located in western France with a total traffic of just under 200,000 passengers per year, is owned and operated by the local Chamber of Commerce.

"The Chamber of Commerce received subsidies of approximately 3 million euros (4.0 million U.S. dollars) between 2002 and 2005 from various public bodies to finance various infrastructure projects at La Rochelle airport," the Commission said in a statement on its website.

"The Commission will verify whether the subsidies were necessary to carry out the investment, whether the aid was proportionate to the objectives pursued and whether the infrastructure had satisfactory medium-term prospects for use," said the statement.