"We have found no evidence that he was part of an Islamist cell," local police vice president Petra Sandles told journalists at an emergency press conference.
Criminal director Loothar Koehler said the 27-year-old, a German citizen from the central state of Hesse, had not been known by German intelligence agencies to have "any form of connection to Islamist or Salafist groups." Neither was he influenced by Islamist propaganda videos, Koehler added.
German media mentioned unconfirmed witness reports that the attacker had shouted "Allahu Akbar" ("God is great" in Arabic) as he attacked commuters at an S-Bahn station in Grafing. Four people were injured, one of them died of his wounds.
Germany’s Federal Interior Minister Thomas de Maiziere described the knife attack as an "awful, cowardly" act. He said no definitive motive of the assault had been established.
Prosecutor's office spokesman Ken Heidenreich said the man faces criminal charges of murder and attempted murder. The criminal process is due to start on Wednesday.
