The European Commission is preparing an in-depth antitrust investigation into UPM and Sappi's planned graphic paper joint venture, valued at approximately 1.4 billion euros, according to reports.

A decision is expected following the preliminary review on April 28.

The deal, which merges operations across several European countries and the United States, faces scrutiny over competition concerns in a strained industry grappling with declining demand and high energy costs.

The companies may be forced to offer concessions, such as asset divestments.