Thirty people - many of them children - were injured when a man drove his car into a carnival parade in Germany yesterday.
Police believe the incident in the small town of Volksmaren, near Kassel, was premeditated.
Seven of the victims were seriously injured, including children.
The driver is a 29-year-old German citizen who has not been named under the country's privacy laws.
He is understood to be from the local area, and has no history of political extremism.
"We don't think this was a terror attack. We're assuming it was an intentional crime," a police spokesman told reporters.
But the regional government said a terror attack "could not be ruled out", given the facts on the ground.
There were conflicting claims over the driver's condition last night. There were unconfirmed reports he had been taken to a psychiatric clinic.
Prosecutors denied reports he could not be questioned because he was seriously drunk.
"He was not drunk and cannot be questioned because of his injuries," said Alexander Badle, a spokesman for the prosecutors.
But a woman claiming to be a neighbour of the man told German television he appeared to be under the influence of drugs.
"I saw him drive away today. He looked like he was on drugs and said: 'I'll be in the newspaper soon'," she told RTL TV.
There were unconfirmed reports of a second arrest last night, but the details were unclear. The incident took place at around 2.30pm as families were taking part in a traditional Rose Monday carnival parade.
Witnesses described a silver Mercedes estate car racing into the crowd. It travelled some 30 yards before coming to a stop.
Witnesses claimed the driver appeared to target children deliberately, and swerved to avoid a barrier before ploughing into the crowd.
After the car came to a stop, bystanders attempted to attack the driver and he had to be protected by police.
"It was a beautiful procession and just as it ended I suddenly saw flashing lights and heard sirens," Reinhard Kubat, a local councillor, told 'Bild' newspaper.
"Crying people came towards me.
"There were mainly injured children on the street, but also older people."
"When I arrived there were 15 people on the floor, many of them small children," Elmar Schulten, a reporter for the local 'Waldeckische Landeszeitung' newspaper said.
"People were howling everywhere, including grown men. Fathers saw their children lying on the floor."
Volksmaren, a small town of 6,800 in the central state of Hesse, was in deep shock.
All access roads were sealed off, and police requested local people not to share any photographs they had of the scene on social media.
Police in the city of Mainz ordered drones to fly near large events in order to monitor suspicious car movements.
Police presence is already heightened across Germany in the wake of a series of attacks.
The latest incident comes just days after a far-right gunman killed nine people before turning his gun on his mother and himself in Hanau, which also lies in Hesse.
Carnival celebrations were cancelled across Hesse in respect for the victims of yesterday's incident.
"We hope they will all make a swift and full recovery," Heiko Maas, the German foreign minister, said on Twitter.
"I am shocked by this bad deed, which has injured so many innocent people, some of them seriously," said Volker Bouffier, the regional prime minister of Hesse.
© Daily Telegraph, London