German investigators said that an Islamist extremist motivation for last week’s fatal knife attack in Wuerzburg appears likely, but they have not so far found any propaganda or other extremist material.
They also plan more checks on the suspect’s mental health.
Friday’s assault in and outside a store in the centre of the Bavarian city left three women dead and another six people seriously injured.
The suspect, a 24-year-old Somali man, was shot in the leg by police and arrested after people surrounded him and tried to hold him at bay with chairs and sticks.
Officials have said they believe the suspect was a lone assailant.
He was sent to jail on Saturday pending a possible indictment.
Bavarian extremism and terrorism investigators took over the case on Saturday because an Islamist background appears likely, Munich prosecutors and Bavaria’s state criminal police office said in a statement.
They said that is supported by witnesses’ account that he twice shouted “Allahu akbar”, the Arabic phrase for “God is great”, and also referred to “jihad” after his arrest.
Investigators are still evaluating objects that were seized at his accommodation, including two mobile phones, but have not yet found signs of propaganda or extremist material, they added.
They also plan to order a psychiatric evaluation of the suspect to determine whether he can be held criminally responsible for his actions and whether he needs to be sent to a psychiatric hospital or rehabilitation clinic.
Prosecutors have said there were two incidents earlier this year that resulted in him being sent briefly to a psychiatric hospital.