One person was stabbed to death and nine others injured by a knifeman outside a station near the French city of Lyon, before police managed to detain him.
Authorities said the reason for the attack was unclear.
The attacker was a 33-year-old Afghan citizen who had applied for asylum in France and was awaiting a response, according to a national police official.
The attacker provided contradictory information to police, but the attack did not appear to be terrorism-related, two French officials told The Associated Press.
The victim who died was a 19-year-old man, and it was unclear if he knew the attacker, according to police.
Police initially launched a manhunt for a second attacker but later determined that the detained man was the main suspect, the security official said.
The official told The Associated Press that police were still looking for possible accomplices.
The national anti-terrorism prosecutor's office has not been asked to take part in the investigation at this stage.
An official with the Lyon regional administration said national security forces were not involved in the search, which include local police officers and a helicopter.
France remains on high alert after several deadly Islamic extremist attacks in 2015 and 2016.
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