German prosecutors have carried out searches in connection with their investigation into the Volkswagen emissions scandal, seeking material that would help clarify who was responsible for the cheating.
The raids were carried out in Wolfsburg, where VW has its headquarters, and at other locations, prosecutors in nearby Braunschweig said in a statement.
They said the aim of the searches was to "secure documents and data storage devices" that could identify those involved in the alleged manipulation and explain how it was carried out.
Prosecutors last week launched an investigation to determine who was responsible for suspected fraud committed through the sale of vehicles with manipulated emissions data. They acted after receiving about a dozen criminal complaints from citizens and one from VW itself.
Longtime chief executive Martin Winterkorn resigned after the scandal broke in the US on September 18, saying that he was not aware of any wrongdoing on his part. He was replaced by Porsche boss Matthias Mueller.
Volkswagen has suspended four individuals, including three managers who were responsible for engine development, and hired US law firm Jones Day to conduct an investigation.
Earlier, Germany's vice chancellor travelled to Wolfsburg to send a message of support to the carmaker's employees, and urged the company to be proactive in its efforts to clear up the scandal.
Sigmar Gabriel, who is also Germany's economy minister, joined a meeting of employee representatives from Germany and beyond as Volkswagen tries to determine who was responsible for the installation of test-cheating software and how quickly up to 11 million vehicles that potentially contain it can be fixed.
"I think it is important to send the message that, in the end, the employees must not pay the price for ... criminal behaviour by managers," Mr Gabriel said in Wolfsburg.
"It is clear that the company must clear this up - the more offensively it does so, the better," Mr Gabriel said. "The more defensively it approaches the question, the more difficult it will be. My impression is that the supervisory board and the new CEO know this."
The company says a recall of cars with the suspect software could start in Germany in January and last until the end of next year. On Wednesday, transport minister Alexander Dobrindt said the carmaker said in reply to German authorities' demand for a timetable that there would be a recall for vehicles with 2-litre, 1.6-litre and 1.2-litre engines.
VW said the 2-litre engines will need a software update that should be ready before the year's end and be installed from the beginning of 2016, according to Mr Dobrindt. He said 1.6-litre vehicles will need "an engineering modification that according to Volkswagen shouldn't be expected before September 2016".
There are some 3.6 million 1.6-litre cars in Europe, Mr Dobrindt said. He did not say what fix 1.2-litre cars will require.
The software in question, known as a "defeat device", is capable of turning on pollution controls for lab tests and shutting them off during real-world driving. German daily Sueddeutsche Zeitung reported on Thursday that VW apparently used it for that purpose in Europe as well as the US.
Volkswagen said in an emailed response to questions about the report that "whether and to what extent this software actually intervenes improperly is currently still the object of internal and external tests". The company added that it is also not yet clear whether the software was banned under European rules.