FRANKFURT — An investigation into Volkswagen’s diesel emissions scandal expanded significantly on Thursday after German authorities arrested a former high-ranking executive of the carmaker, two people with knowledge of the arrest said.

The executive, identified by German news outlets as Wolfgang Hatz, is a former chief of engine development at Volkswagen. He worked closely with Matthias Müller, now the company’s chief executive, when both were members of the management board of the carmaker’s Porsche unit. Mr. Hatz was being held in Munich without bail.

Mr. Hatz, well known in automotive circles because of his previous role as chief of research and development at Porsche, is the second person to be arrested in Germany in connection with the Volkswagen case and the first German citizen. His prominence signals that the investigation — which has proceeded slowly since the wrongdoing came to light two years ago — may be entering a more intense phase.

Being incarcerated puts Mr. Hatz under enormous pressure to testify against others because his chances of winning release are greater if he cooperates. The information he provides could lead to new revelations and seriously impede Volkswagen’s attempts to put the scandal, in which it admitted to manipulating diesel cars so they artificially reduced their emissions in lab tests, behind it.