PARIS -- French police have questioned another batch of tennis players in a growing investigation into a match-fixing syndicate suspected of paying out hundreds of thousands of dollars to fix low-level matches, judicial officials said Thursday.

Seven French players were taken into custody this week and later released, taking the total number questioned in France so far to at least 17, the officials said. An initial batch of four players was first questioned in January . The officials spoke on condition of anonymity because they aren't authorized to publicly discuss the investigation.

The probe is being led by authorities in Belgium, where the syndicate's suspected ringleader, an Armenian, is based. Belgian authorities say Grigor Sargsyan remains in custody in his home, monitored with an electronic bracelet.

Investigators say corrupted players bought off by the fixers knew Sargsyan as “Maestro.” The massive scheme, organized via encrypted messaging and involving dozens of low-ranked players in small tournaments with little prize money, is believed to have spread tentacles to more than a half-dozen countries, including the United States. Belgian authorities say they've requested assistance from the FBI, as well as counterparts in Egypt, Slovakia, Bulgaria, the Netherlands and Germany.

This week's additional detentions were first reported Thursday by French sports daily L'Equipe. Officials didn't identify the players.

A Belgian investigator said five of the French players questioned so far have admitted to taking money from the syndicate to fix matches, and that one player believed to have fixed about two dozen matches confessed to police that he pocketed 30,000 euros ($ 34,000).

The probe has grown far bigger than Belgian authorities initially expected when they first swept up Sargsyan and others in a wave of arrests in June. He faces organized crime, match-fixing, money laundering and forgery charges.

In all, more than 100 players are suspected of having worked with the syndicate, fixing matches, sets or games in exchange for payments of 500 to 3,000 euros ($570 to $3,400). Police say the syndicate employed mules, people hired for a few dollars to place bets on fixed matches that were small enough to slip under the radar of gambling watchdogs.

The Belgian investigator said evidence collected so far suggests that the syndicate knew other match-fixers in Spain but they weren't working together.

So far, France has the biggest number of players questioned in the probe. The first four were named by investigators as Jules Okala, 21; Mick Lescure, 25; Yannick Thivant, 32; and Jerome Inzerillo, 29. None operated in the highest spheres of tennis. The career-best singles ranking of any of them was 354, reached by Inzerillo in 2012.

L'Equipe said it interviewed Inzerillo, accompanied by his lawyer, this week and that he told the newspaper that he had never been approached to fix a match.