PARIS (AP) — Two retired members of the French secret services suspected of being double agents for an unnamed foreign power have been handed preliminary charges along with a suspected accomplice, French authorities said Friday.

President Emmanuel Macron said that France's foreign intelligence agency DGSE detected "actions of extreme gravity" by the former DGSE agents.

Macron, speaking during a visit to Russia, said Paris prosecutors are investigating. He would not comment on a report that the agents had been working for China.

The investigation was opened last year but the Defense Ministry only confirmed it Thursday after details of the probe were reported Thursday on TMC television.

The two men were given preliminary charges in December including compromising defense secrets and "delivering information to a foreign power that threatens fundamental interests of the nation," according to a judicial official. The official said one of the men was also given preliminary treason charges.

The two are being held in custody pending further investigation and a decision on whether to send them to trial.

A third person was given a preliminary charge related to treason, but released under judicial supervision, the official said. The official was not authorized to be publicly named.

The official didn't identify the third person, but the Defense Ministry said the wife of one of the men was also suspected to be involved.

Defense Minister Florence Parly, speaking on CNews television, said their actions could "potentially compromise state security."

The ministry did not specify for which country the agents are suspected to have worked.

News and entertainment show Quotidien, which first reported the news on TMC television Thursday night, reported without citing sources that the agents were working for China and that one of them was based in Beijing.