X has yet to respond. BBC news has approached the company for comment.
It has previously described the investigation as an attack on free speech.
In its statement, the prosecutor’s office said the operation formed part of efforts to ensure X complied with French laws.
It said the probe, led by French cyber-crime police, was expanded in July 2025 after reports of sexually explicit deepfakes and holocaust denial content circulating on the platform.
X previously described the widening of the probe in a post at the time, external as “politically-motivated” and denied allegations it had manipulated its algorithm.
The prosecutor’s office also said it was leaving X and would communicate on LinkedIn and Instagram from now on.