Siemens AG and French rival Alstom SA were formally warned by European Union regulators of potential antitrust problems with their train merger.

Officials at both companies confirmed Oct. 31 that they received the document with the EU’s concerns, formally known as a statement of objections.

Key Insights

  • The deal, backed by the French and German governments, would combine the two biggest train makers on the continent to create a European rail giant. The companies argue that this is the best...