Exact figures for the missing total are unclear, but it could amount to the biggest scam by commission officials in its 40 year history, and the first in which civil police have been called in to handle a large investigation.
The arrests of George Tzoanos, the Greek former head of the commission's tourism unit, his wife and a Frenchman named Pascal Chatillon, who worked on a temporary contract for the unit, follow a nine-month investigation by the Belgian fraud squad, involving checks on travel companies and tourist organisations across Europe.
Both men are alleged to have received kickbacks from companies in return for channelling subsidies to promote tourism to them. In some cases the projects never existed.
The two men were suspended from duty nearly two years ago. Although they were later sacked after an investigation by commission officials last autumn, the case is likely to raise new questions about European bureaucracy's accountability.
Police became involved only after they were invited to investigate by British Conservative MEP Edward McMillan- Scott. He issued a formal complaint after the commission failed to do so.