An attack on motorists in the western town of Limburg is being investigated as terrorism, security sources have told German media.
On Monday, a man hijacked a lorry and ploughed into eight vehicles waiting at a traffic light, injuring eight people. Seven were treated in hospital.
A thirty-two year-old suspect has been arrested.
Originally from Syria, he has been living in Germany since 2015, local reports say.
Public broadcaster ZDF quoted sources as saying the incident was being treated by investigators as having a “terrorist background”, although Interior Minister Horst Seehofer said on Tuesday he could not yet say how the incident was being classified.
Police searched a flat in Langen south of Frankfurt early on Tuesday and said it was linked to what had happened in Limburg, local reports said.
The owner of the stolen lorry told the Frankfurter Neue Presse (FNP) newspaper that he had been dragged from his vehicle by the man, who had forced the door open.
“What do you want from me?” the driver said he asked the man. “He didn’t say a word. I asked him a again and then he dragged me out of the lorry.”
Another witness, Bettina Yeisley, described talking to the hijacker afterwards without realising he had driven the lorry.