Three French police officers were arrested on Tuesday over the death of a 27-year-old man in the southern city of Marseille in early July during nationwide rioting, prosecutors said.
France was convulsed in late June and early July by violent rioting over the killing outside Paris on June 27 of a teenager by a policeman during a traffic check.
The riots were met by a forceful police response.
Hundreds of people were arrested and hundreds of police officers were wounded.
But there had not previously been any confirmation of a member of the security forces or a protester losing their life during the events.
In all, five police officers from the elite Raid unit were taken into custody on Tuesday morning in Marseille for questioning in the probe over the death of Mohamed Bendriss, prosecutors said.
Two of the five were released in the early evening, the public prosecutor's office announced.
"The other three police officers remain in custody," confirmed Marseille public prosecutor Dominique Laurens.
Several civilians and police are also giving evidence as witnesses, the prosecutors added.
The incident took place during the night of July 1-2 during violent protests in the centre of Marseille sparked by the death of Nahel M., 17, who was shot dead by a policeman on June 27 during a traffic check.
- Widow expecting second child -
Bendriss, a married father of one, whose widow is now expecting a second child, lost his life after feeling unwell while riding a scooter.
His autopsy showed traces on his chest of what could be the impact of a shot from a blast ball and commonly used by the country's police.
The prosecutor's office has said it considers it "probable" that the man's death was "caused by a violent impact to the thorax caused by the firing of a projectile of the blast ball type".
The investigation is the latest controversy to target Marseille police.
Earlier this summer, a 22-year-old man called Hedi had to have part of his skull amputated after being beaten up and fired on with a blast ball on July 21 by a group of men suspected to be police officers.
Four Marseille police officers have been charged over the incident.
Three have been released under judicial supervision.
The fourth has been remanded in custody for the duration of the investigation. His detention caused huge controversy within the French police.
Officers across the country went on sick leave en masse as a sign of protest but a court last week rejected the appeal against his detention.
The officer admitted in court to firing a blast ball round, reversing an earlier denial, but said he did not see anybody injured. His lawyer added that there was no proof it was his round that had wounded Hedi.
The powerful police union, Alliance, said the ruling was "incomprehensible and very unfair".
A total of 31 investigations by the IGPN police investigation unit were opened during the riots, a police source told AFP.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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