The cheating has become a political issue, with European governments accusing one another of weak enforcement. The European Union has charged the Italian government with allowing Fiat Chrysler to sell cars with software intended to evade emissions tests, and it has begun investigating possible oversights in other countries, including Britain and Germany.
In the case of Daimler, prosecutors in the German city of Stuttgart said they had raided 11 of the company’s locations, searching for digital and analogue documents that could serve as evidence in their investigation of allegations of fraud and illegal advertising in connection with the company’s diesel cars.
Twenty-three prosecutors, working with 230 state and local police officers, carried out the raids across Germany, including in Baden-Württemberg, where Daimler has its headquarters; in Berlin; and in the states of Lower Saxony and Saxony, the authorities said in a statement.
They did not release any further information about who might be the target of their investigation, saying only that they were “known and unknown” employees.
In a separate statement, Daimler said the raids were because of “suspicion of fraud and criminal advertising relating to the possible manipulation of exhaust-gas aftertreatment in passenger cars with diesel engines.”
The company said it was cooperating with the office of the Stuttgart public prosecutor, but it did not comment further.
Daimler is facing other investigations. The Department of Justice in the United States had requested that the company conduct an internal inquiry, the carmaker said in its first-quarter report. The company also said that the Environmental Protection Agency in Washington, the California Air Resources Board and the Securities and Exchange Commission had requested information.
The raids on Tuesday came a day after Chancellor Angela Merkel of Germany joined Dieter Zetsche, Daimler’s chairman and head of its Mercedes-Benz division, to lay the cornerstone for a new factory to build batteries.
The German auto industry has long lagged behind its competitors when it comes to developing electric cars, choosing instead to focus on diesel technology as a cheap and efficient energy source.
But revelations in 2015 that Volkswagen’s diesel vehicles had used a “defeat device” — software that can detect whether a car is on the road or being tested in a lab, and alter emissions levels accordingly — prompted an examination of whether other German automakers had also been cheating on emissions tests.
Unlike Volkswagen’s use of a defeat device, Daimler’s Mercedes division, along with the German engineering company Bosch, developed a different technology that relied on using an additional fluid to meet emissions standards.
Known as AdBlue, the fluid was made of a chemical called urea that mixed with engine exhaust to neutralize nitrogen oxide, one of the most harmful diesel pollutants.
Deutsche Umwelthilfe, an environmental advocacy group in Germany, has charged that Mercedes cars turn off the system, which is known as BlueTec, when the temperature drops, leading to increased pollution levels.
An earlier version of this article referred incorrectly to the fluid used in a Mercedes engine system to meet emissions standards. It is AdBlue, not BlueTec, which is the name of an engine system.