BERLIN (AP) — German prosecutors said Monday they now believe that the suspect in a knife attack on a train in November that left four people wounded had an Islamic extremist motive.

The attack took place on an ICE high-speed train traveling from Passau, on the Austrian border, to Hamburg on Nov. 6. Authorities said that the man attacked his victims apparently at random and showed signs of mental illness, but initially said there was no immediate indication of a terror motive.

Munich prosecutors said a few weeks later that they were no longer ruling out an Islamic extremist motive.

On Monday, they said that investigations have produced “weighty indications” that the suspect's actions were based on support for the Islamic State group's ideology, though there was no evidence so far that he was involved with or “steered” by the group.

An expert has concluded that the man could be held criminally responsible for his actions, and he was sent to jail in January. Federal prosecutors, who handle terrorism and national security cases in Germany, have now taken over the investigation.

Police have said that the suspect, a Syrian citizen, came to Germany in 2014 and was granted asylum in 2016. He had been living in Passau.