Police in the German town of Volkmarsen on Monday arrested a 29-year old man after a car plowed into a crowd of people at a parade and injured at least 30 people.

Police said that the suspect, a German citizen from Volkmarsen, was receiving medical treatment for "the injuries he suffered in connection with the incident" and would be brought before an investigating judge when his health allows, CNN reported.

Eyewitnesses said the car "intentionally" rammed into the crowd of carnival celebrants at around 2:30 p.m. local time (8:30 a.m. ET).

The interior ministry of the federal state of Hesse said in a statement that the suspect ''drove at high speed." It added that the man in the custody ''is currently not interrogatable."

"Due to the situation on site, an attack currently cannot be ruled out," the statement added.

The ministry said that a special unit had been set up in the Frankfurt Police Headquarters to investigate the incident, and that the police presence had been strengthened across Hesse.

All carnival events across Hesse were canceled on Monday after the incident in Volkmarsen. North Hessen Police said the move was a precaution.

Elmar Schulten, a reporter for the local newspaper Waldeckischen Landeszeitung, told CNN the incident happened near the town's train station.

He said he "saw a silver Mercedes had broken through the police blockage" and "headed directly to the crowd."

"I counted up to 15 people laying in the street and the walkway. Several small children laying and crying," Schulten added. At least four or five helicopters were picking up patients from the site, he said.

Volksmarsen is a small town with roughly 6,000 residents, located near Kassel, in the north of the federal state of Hesse in central Germany.

Schulten said the carnival parade is a tradition in the town, with some 30 floats and 1,000 people taking part. He estimated that more than 5,000 people were watching in the streets.

The motive for the incident is not yet clear. Germany has been on a high level of alert due to a series of terrorist attacks in the country in recent years.

One of the most serious attacks was a 2016 attack on a Christian market in Berling in which 12 people were killed by an Islamic State (ISIS) terrorist who rammed into a crowd of civilians.

In January, six people were killed and another two wounded in a shooting in the southwestern German town of Rot am See. Police said they believed that incident was “family drama” and not an act of terrorism.

Last week, 10 people were shot dead in two shisha bars in the German city of Hanau, located near Frankfurt.

Hanau, a city in southern Hesse, was the site of a deadly shooting attack by a suspected far-right extremist last week.

Police in Mainz, a city in the neighboring state of Rhineland-Palatinate, said security at the carnival event happening there on Monday had been tightened, with surveillance drones deployed.