In an announcement Tuesday, the commission said it will look at whether the combination of thyssenkrupp’s steel division and Tata’s European flat-rolled assets may “reduce competition in the supply of various high-end steels.”

“Steel is a crucial input for many of the goods we use in our everyday life, and competitive steel prices are vital for the European economy. Industries dependent on steel employ over 30 million people in Europe and we must be able to compete in global markets,” said Commissioner Margrethe Vestager. 

"This is why we will carefully investigate the impact of the planned combination of Tata Steel's and thyssenkrupp's steel businesses on effective competition in the steel markets."

The in-depth investigation follows a preliminary inquiry that raised market concerns regarding galvanized automotive steel, metallic coated steel for packaging, and grain-oriented electrical steel. 

“At this stage, the commission is concerned that, following the transaction, customers would face a reduced choice in suppliers, as well as higher prices,” the commission said. 

The BBC has more coverage here.