A man apparently armed with a knife attacked passengers on a busy bus Friday in the northern German city of Luebeck before being overpowered and arrested, authorities said. Nine people were reported injured, one seriously.

Authorities had no immediate information on the assailant’s motive for the attack on a city bus in Luebeck, which is near the Baltic coast northeast of Hamburg.

Prosecutor Ulla Hingst told n-tv television the bus driver stopped the vehicle and let the passengers out after the attack. She said the weapon used was apparently a knife, but that is still under investigation.

Experts were also examining a backpack on the bus as a precaution. Hingst said it wasn’t clear whether it belonged to the suspect, but said there had been reports of smoke coming out of it.

She said the identity of the suspect, who was being questioned by police, has yet to be confirmed.

“The background to this act is completely unclear,” she said. “We are investigating in all directions. We cannot currently rule anything out.”

Schleswig-Holstein’s state interior minister, Hans-Joachim Grote, said his information was that nine people were injured — six with the knife, two passengers who fell and the driver, who was punched.

Police said in a statement released at the same time that one of the injured was seriously hurt, but said the total number of injured wasn’t initially clear.

The bus was traveling from Luebeck to the neighboring seaside resort of Travemuende, where an annual regatta, the Travemuender Woche, was opening later Friday.

Grote said, at present, authorities believe security for the regatta is sufficient.

(AP)