(Telecompaper) The European Commission is investigating whether Apple is muscling out rival smartphone makers from the market with anti-competitive iPhone sales tactics and technical restrictions on the handset, according to documents seen by the Financial Times. According to a questionnaire sent to several EU mobile operators, the Commission's probe is focusing on distribution terms. The inquiry was prompted by complaints from mobile operators and remains at a preliminary stage. Before launching a formal probe, the commission will need to be confident that Apple is dominant in the EU smartphone market. Apple says its contracts fully comply with EU laws. The nine-page questionnaire primarily relates to sales practices, including whether Apple forces groups to buy a minimum number of iPhones, restrictions on the use of marketing budgets, and clauses that ensure Apple is always offered no worse subsidies and sales terms than other smartphone makers. It also asks whether Apple places technical or contractual restrictions on the iPhone 5 that mean it cannot be used on 4G networks in Europe.