A hijacked truck rammed into cars and injured eight people in the German city of Limburg last night.
Police are probing if the incident is linked to terrorism.
The driver, who was also injured, has been arrested. He has been identified in local press as a 32-year-old man originally from Syria who moved to Germany in 2015.
The man shouted "Allah!", German media has quoted witnesses as saying.
Some 60 riot police officers stormed into an apartment that is believed to belong to the man at 1am today.
Did you see what happened? Email webnews@mirror.co.uk
"Based on what we have learned and several witness accounts, the man seized control of the truck at about 5.20 pm (1520 GMT)," police said in a statement.
According to police, the lorry slammed into eight cars that were waiting at a traffic light near the main railway station of Limburg in Hesse state, "crushing them together".
Several people were being treated in hospital.
A spokesperson for West Hesse police said they were looking into all motives behind the incident, but added: "We currently do not have sufficient information about what was behind it."
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.
The police have said it was normal procedure for the driver to be arrested in such circumstances.
Police deployed officers and a helicopter following the incident in the German city of 35,000 inhabitants.
This morning the site is still being assessed by police investigators.
The truck has been towed.
The Mayor of Limburg, Marius Hahn, told the German Press Agency: "I am shocked and in my thoughts with the injured accident victims and their families."