The Commission said on Thursday its officers had raided several companies involved in making and selling consumer electronics and small domestic appliances, concerned that the firms had worked together to limit the sale of some goods online to drive up their prices. It did not give the names or locations of the companies inspected by its officers on December 3. The investigation comes as traditional electronics retailers wage a fierce battle with online rivals such as Amazon. The EU antitrust regulator can fine companies up to 10 percent of their global revenue for breaking EU rules. All three companies said they were cooperating with the EU authorities, but declined any further comment.