Berlin/Washington, Dhu-AlHijjah 24, 1436, October 08, 2015, SPA -- Police raided embattled German carmaker Volkswagen's offices and several employees' homes on Thursday as prosecutors stepped up their probe into the exhaust emission tests scandal that has rocked the group, according to dpa. VW's head office in the northern German city of Wolfsburg along with residences and offices across the nation were searched, the public prosecutor in the nearby city of Braunschweig said. About 50 police officers and three state prosecutors conducted the searches, which followed the carmaker's admission about three weeks ago that it had equipped its diesel-powered vehicles with software aimed at cheating on emission tests. "The raids were aimed at securing documents and data storage devices that, in view of possible offences, can provide information about the conduct of company employees and their identities in the manipulation of exhaust emissions of diesel vehicles," prosecutors said. VW, which has launched it own independent inquiry into the scandal, said it was doing all it could to assist the prosecutors in their investigation. The raids came as VW US chief Michael Horn appeared before a US House of Representatives committee to answer questions on the scandal. Horn apologized for the company's manipulation of the emissions tests but said he was unaware of the software until last month. He said he became aware of an "emissions issue" after a West Virginia University study was published in May 2014 but thought VW engineers would find a way to fix it. Horn went on to say that he had "no reason to believe there was a defeat device in those cars." Calling the affair "deeply troubling," Horn said that of the 500,000 VW vehicles affected in the US, 430,000 will require more than a software fix. Horn testified that to date three employees had been suspended in wake of the scandal. Throughout his appearance, Horn faced a barrage of criticism and skepticism. "VW will inevitably pay a steep price for this dirty little secret," Republican Fred Upton of Michigan said. The company has "betrayed a nation, a nation of regulators, loyalists, suppliers and innocent customers. It's time to clean it up or get off the road," Upton added. Republican Chris Collins of New York voiced his skepticism that the emissions trickery was the work of "rogue engineers," and wondered if management at "the highest levels" may have been involved. VW has withdrawn its application to US regulators to certify its 2016 models pending full disclosure of all aspects of their emission systems, Horn said. Earlier in the day, German Economics Minister Sigmar Gabriel visited VW's Wolfsburg factory in attempt to reassure workers, who have concerns about the affair's impact on their jobs. "I think it is important to send the message that the employees must not pay the price for the criminal behaviour of managers," he told the employees. Prosecutors around the world have also launched investigations into VW in the wake of the scandal. Since then, the company has revealed that about 11 million vehicles around the world were fitted with the software. VW said about 2.8 million of the vehicles are in Germany with the group likely to face compensation claims and fines running into the billions as a result of the affair. The scandal has already resulted in the resignation of VW group chief executive Martin Winterkorn, but it remains unclear who was responsible for ordering the company to develop the emission-test-evading equipment and for installing it. The company last month appointed the head of VW's luxury sports carmaker Porsche, Matthias Mueller, to take over as the group's new chief to help steer the auto manufacturer out of the crisis. --SPA 23:45 LOCAL TIME 20:45 GMT www.spa.gov.sa/w