The European Commission has contacted mobile operators to discuss whether Apple’s iPhone distribution deals could be aimed at shutting out rival smartphone makers, reports said.

Apparently, the antitrust regulators have sent a “nine-page questionnaire” to unspecified operators, following informal complaints related to the iPhone maker’s subsidy and marketing strategy.

According to Reuters, the document sent to operators includes the sentence: “The Commission has information indicating that Apple and mobile network operators have concluded distribution agreements which may potentially lead to the foreclosure of other smartphone manufacturers from the market.”

Among the information sought is whether Apple has imposed minimum purchase commitments on operators, demanded preferential treatment in marketing efforts, and set the subsidy level to ensure the US giant gets the same or better terms than rivals.

And Reuters also said that regulators are looking to see if Apple restricted companies from using the iPhone 5 with their LTE networks.

The Financial Times said that before launching a formal probe, the Commission will need to be confident that Apple is “dominant” in the European smartphone market, which may prove challenging taking into account Samsung’s strong position in this region.

This is not the first time the European authorities have been reported to be looking at Apple’s practices. In March 2013, it was said that the Commission was “actively monitoring developments in this market”.

However, as yet no operator is believed to have made a formal submission against the device maker. But as the EC’s recent threat of action against Chinese vendors has shown, the watchdog is not completely against taking action on its own initiative.

According to figures from IDC, in the first quarter of 2013, Apple was the second largest smartphone vendor, with market share of 17.3 per cent, behind Samsung with 32.7 per cent, but well above third-placed LG’s 4.8 per cent.

The company is also the third largest handset maker overall, with 8.9 per cent market share, behind Samsung (27.5 per cent) and Nokia (14.8 per cent).

Operators have until 17 June to reply to the questions, the FT said.