HAMBURG (Reuters) -- Volkswagen believes that up to around 20 people were involved in its rigging of diesel-engine emissions tests, a person familiar with the matter said on Thursday.
A source told Reuters earlier this month that more than ten senior managers had been suspended during an internal inquiry at the German company. Sources have provided the names of six suspended top managers including three brand executives.
"The number of people responsible will not be confined to a handful," the person said, declining to be identified because the matter is supposed to be confidential. "This should be a two-digit number in the range of between 10 and 20."
Europe's biggest carmaker admitted last month to violating diesel emissions tests in the United States, triggering a crisis that has wiped more than a quarter off its stock market value, forced out its long-time CEO and rocked both the global auto industry and German establishment.
VW's U.S. chief, Michael Horn, sparked criticism from some lawmakers earlier this month by saying he believed "a couple of software engineers" were responsible.
The number of people involved is a key issue for investors because it could affect the size of potential fines and the extent of management change at the company.
VW's internal investigation is currently focusing on as many as 40 employees involved in activities related to the manipulations, the person said.
"This includes a number of people who can be ruled out as perpetrators but who were witnesses," the person said. He did not say whether any of the individuals included board members.
VW declined to comment.
Prosecutors from Braunschweig, close to VW's home town of Wolfsburg, are investigating several people on initial suspicion of criminal offenses such as fraud or violation of competition rules, a spokesman said.
Earlier this month, the prosecutors raided VW's Wolfsburg headquarters and other offices, targeting documents and data storage devices.
VW has hired consultants Deloitte to support an investigation into the scandal by U.S. law firm Jones Day, with new Chief Executive Matthias Mueller saying those responsible would face tough consequences.
Investigators are looking into documents and computer files dating back as far as 2005 when VW took steps to push diesel-engine technology in the United States as part of a drive to improve its performance in the world's then largest auto market.
VW said on Wednesday it had set aside $7.3 billion (6.7 billion euros) to cover initial costs related to the scandal, but added it did not know what the final bill would be. Some analysts have said it could reach 35 billion euros in regulatory fines, lawsuits and vehicle refits.