PARIS (AP) - An Afghan man was in a "psychotic state" and on drugs during a multiple stabbing in France that killed one person and injured eight others, but investigators have not uncovered any terrorist ties, a regional prosecutor said on Sunday (Sept 1).

A psychiatric evaluation of the man in custody revealed he was experiencing "paranoid delirium" during Saturday's attack, prosecutor Nicolas Jacquet said.

The suspect reported he "heard voices" telling him to kill, according to Jacquet.

A 19-year-old man died after being stabbed with a knife in the attack outside a subway station in the Lyon suburb of Villeurbanne.

Passers-by surrounded and apprehended the assailant before police arrived, according to the prosecutor. He thanked them.

"Their courageous, responsible intervention was decisive," Jacquet told reporters.

A witness that broadcaster BFMTV identified as "Sofiane" described trying to help people who were stabbed and rounding up others to go after the attacker.

The man in custody has been living in a French centre for asylum-seekers, Jacquet said.

He held a temporary French residency card and first registered in 2009, the prosecutor said.

The man subsequently travelled to Britain, Italy, Germany and Norway.

After the stabbings, the suspect gave "incoherent" accounts and three different dates of birth to police, Jacquet said.

The man was not publicly named, but he was not on any radicalism watch list, Jacquet said.

Officers went to the suspect's residence to look for signs of extremism and during their search "nothing was found showing any kind of radicalisation," he said.

The suspect had no police record or record of psychiatric problems, the prosecutor said. He was found with two knives but no other weapons.

Two of the eight people injured remained hospitalised. French police initially said nine people had injuries but the prosecutor said the total was eight. The reason for the discrepancy was unclear.

Villeurbanne Mayor Jean-Paul Bret said the man held is the only person suspected of wielding the knife.

The mayor also called anti-migrant politicians "shameless" for seizing on the stabbings to push their views.

French far-right leader Marine Le Pen tweeted after the attack that "lax migration policy" threatens France's security.

The attack raised concerns because France remains on alert after a string of deadly Islamic extremist attacks.