The $1.5 billion deal would create the world's second largest heavy truck maker.
The commission will extend its initial four week probe into the case by two weeks, according to the Associated Press. By Sept. 6, the EU's executive commission must decide whether to approve ther merger or to launch an in-depth investigation.
Under the terms of the deal, announced in April, Volvo will pay about $1.5 billion, or about 15% of its shares, to acquire the truck division of Renault SA, including RVI of Europe and the U.S.-based Mack Trucks.
In March, the commission blocked Volvo's proposed $6.9 billion takeover of Swedish rival Scania.