The 69-year-old suspected of shooting dead three Kurdish people in Paris appears before an investigating judge.
Monday’s development came as the suspect appeared before an investigating judge.
The 69-year-old man was arrested on Friday after two men and a woman were shot dead at a Kurdish cultural centre and nearby Kurdish cafe in Paris’ busy central 10th district.
The suspect’s name has not been officially released though he is identified by French media as William K.
Under French law, being put under formal investigation means there is serious or consistent evidence pointing to the implication of a suspect in a crime.
The investigation carried out by a dedicated judge will look into charges of murder, attempted murder and unauthorised possession of a weapon, the prosecutor’s office said in a statement.
It added that it suspected there was a racist motive behind the shootings.
Kurdish representatives have called for the shooting to be considered “a terrorist attack”, saying that police should have done more to protect them.
They have organised a silent protest for Monday afternoon where the shootings took place.
The killings prompted protests that led to clashes with police over the weekend.
Antiracism activists and left-wing politicians have linked the shooting to a climate of hate speech online and anti-immigrant, xenophobic rhetoric by far-right figures.
French authorities have reported a rise in race- or religion-related crimes and violations in recent years.