Qualcomm Inc on Wednesday disclosed that an antitrust investigation that has started around new 5G chips.

The European Union is investigating whether Qualcomm engaged in anti-competitive behavior by leveraging its market position in 5G modem chips in the radio frequency chip market, the San Diego company said on Wednesday in a regulatory filing.

Qualcomm last year lost a case brought by the U.S. Federal Trade Commission and remains locked in an appeal.

Besides making modem chips, Qualcomm is also expanding into a related field called radio frequency front-end chips, which have become more complex in phones that use 5G networks.

Qualcomm has been trying to persuade phone makers to buy its radio frequency chips, together with its own modem chips, rather than selecting parts from separate vendors and integrating them.

Other major suppliers of radio frequency chips are Broadcom Inc, Skyworks Solutions Inc and Qorvo Inc.

In Wednesday’s filing, Qualcomm said it was in the process of responding to a probe by the European Commission, after it served a request for information with the company on Dec. 3.

Qualcomm said the commission could impose a fine of up to 10% of its annual revenue if a violation were found.

Qualcomm was fined 242 million euros by the European Commission in July last year for blocking a rival from the market. The Commission had also fined Qualcomm 997 million euros during 2018 for paying iPhone maker Apple to use only its chips, a tactic aimed at thwarting rivals including Intel.