BERLIN, Dhu-AlHijjah 8, 1436, Sep 22, 2015, SPA -- Volkswagen's chief executive was under withering pressure Monday as an emissions-testing scandal erased more than 13 billion euros (around $15 billion) from the company's market value in a single trading session, according to AP. The stock plunge followed revelations that the German carmaker had rigged U.S. emissions tests for nearly 500,000 diesel cars. VW CEO Martin Winterkorn apologized, acknowledging that his company had "broken the trust of our customers and the public." Investors considering the financial and reputational implications of the scandal on the world's top-selling carmaker dumped VW stock Monday, driving the company's share price down a stunning 17.1 percent in the first trading since the U.S. Environmental Protection Agency announced the violations. VW shares closed at a nearly three-year low of 133.70 euros. VW, facing as much as $18 billion in fines, has halted U.S. sales of the affected vehicles and pledged to cooperate with regulators. The investigation also could test the U.S. Justice Department's resolve, announced Sept. 9, to hold individual executives accountable for corporate wrongdoing. -- SPA 01:16 LOCAL TIME 22:16 GMT www.spa.gov.sa/w