The Paris prosecutor's office said on Wednesday it had launched a preliminary investigation into the US National Security Agency's Prism surveillance programme after French rights groups complained it was snooping on citizens' emails and phone calls.
The probe, which was opened in mid-July, followed a legal complaint earlier that month by two human rights groups denouncing US spying methods revealed by former intelligence contractor Edward Snowden.
The groups filed their complaint against "persons unknown" but named Microsoft, Yahoo, Google, Paltalk, Facebook, AOL and Apple as "potential accomplices" of the NSA and FBI.
The original complaint was filed by the International Federation for Human Rights (FIDH) and the French Human Rights League (LDH).
The prosecutor's office said it had ordered investigating police to examine claims of fraudulent access to an automated data processing system, collection of personal data by fraudulent means and wilful violation of the intimacy of private life.
In a preliminary investigation, police determine whether there is enough evidence to open a formal investigation.
In July, the rights groups said French laws had been violated and called for an investigation into the reports on US surveillance that appeared in Britain's Guardian newspaper, the Washington Post and German news magazine Der Spiegel.