BRUSSELS, July 10 (Reuters) - EU antitrust regulators are set to open a full-scale investigation into Saipem's SPMI.MI merger with Norwegian peer Subsea 7 SUBC.OL because of competition concerns, people with direct knowledge of the matter said.

The companies announced the deal in February last year to create a leading global player in offshore energy services, from drilling and engineering to laying subsea infrastructure for offshore oil and gas projects. Both operate a fleet of vessels for these services.