The European Union(EU) is likely to begin a full-scale antitrust investigation on the planned merger of South Korea's Korean Air and Asiana Airlines.

Citing multiple sources, Reuters reported on Thursday that Korean Air's planned takeover is expected to face a full-scale EU antitrust investigation due to concerns about the merged entity's market power.

The full-scale probe appears to refer to the second-stage investigation on the acquisition.

According to the European Commission, Korean Air submitted a report on its acquisition plan on January 13, two years after it went through preliminary consultations with the EU.

After accepting the report, the EU usually conducts a first-stage antitrust probe on the plan for 35 days, which is set to end on Friday for the South Korean flag carrier.

If the plan fails to win approval in the first stage, the EU regulator will carry out a full-scale probe for up to 130 days. The deal will fall through if it fails to secure approval in the second stage.