Volkswagen (VOWG_p.DE) will name Matthias Mueller, the head of its Porsche sports car brand, as its chief executive, a source close to the matter said on Thursday, as the fallout from the U.S. vehicle emissions test rigging scandal broadened. Mueller, 62, has been widely tipped to succeed Martin Winterkorn, who quit on Wednesday, when the German carmaker’s supervisory board meets on Friday. The crisis deepened on Thursday as officials in Europe and the United States stepped up their investigations.