EU tech regulators will investigate whether online hotel reservation website Booking.com is doing enough to weed out fraudulent listings and phishing scams to comply with EU online content rules, the European Commission said on Wednesday.The Commission, which is the EU tech and competition enforcer, said it opened an investigation following a preliminary probe and after analysing risk assessment reports submitted by Booking.com this year and the previous three years.Big online platforms are required to do more to tackle illegal and harmful content on their sites under the bloc's Digital Services Act, or risk fines of as much as 6% of their global annual turnover for violations.Booking.com said it was engaging constructively with the Commission.