PARIS -- Four tennis players are in French custody on suspicion of helping an organized gambling syndicate believed to have fixed hundreds of low-tier matches, sources close to the investigation told The Associated Press.

The players are suspected of working for Grigor Sargsyan, the 28-year-old known as the Maestro. Police believe the Belgium-based kingpin may have paid more than 100 players from at least half a dozen countries.

The officials, who spoke on condition of anonymity because they weren't authorized to discuss details publicly, said at least one suspect told investigators that he fixed around two dozen matches for Sargsyan.

They named the players as Jules Okala, 21; Mick Lescure, 25; Yannick Thivant, 31; and Jerome Inzerillo, 28. None operated in the highest spheres of tennis. The career-best singles ranking of any of them was 354, reached by Inzerillo in 2012. The arrests of Okala and Lescure were first reported Wednesday by French sports newspaper L'Equipe.

The detentions are part of months of digging by police working across Europe to unravel a massive match-fixing scheme, organized via encrypted messaging and involving dozens of low-ranked players who struggle to make ends meet by playing in small tournaments.

A dozen or more other French players are expected to be questioned in coming days or weeks. An investigator said France was one of the countries "hardest hit" by the syndicate, which targeted lower-level pro-circuit tournaments. Okala and Lescure were detained before they were to play in a modest tournament in Bressuire, France, this week that offers a total of $15,000 in prize money.

Investigators have also questioned other players in Belgium, the Netherlands, Germany, Slovakia and Bulgaria and are looking to question others, including both players and managers, in the United States, Chile and Egypt.

Police say Sargsyan employed mules, people hired for a few euros to place bets for the syndicate that were small enough to slip under the radar of gambling watchdogs.

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), with the deals sometimes organized through encrypted messages.

"The impression we're getting is that it is very commonplace," one official told the AP. Another said several hundred matches are thought to have been fixed.

Investigators fear that players corrupted by the syndicate could suck others into the scheme if left unchecked and could go on to infect bigger tournaments if they climb higher in tennis' rankings.

"In time, they could be managers of other new players or trainers, so we have to get them out of the system or they could corrupt others in a few years," one official told the AP.

Sargsyan was swept up in a wave of arrests in Belgium in June and remains in custody, facing organized crime, match-fixing, money laundering and forgery charges. A suspected banker for the syndicate also faces money laundering and organized crime charges, while four others are being investigated for illegal gambling and finding mules.

Because the bets were small, the risk of detection was "almost zero," but the profits could still be considerable if many bets were placed, one official said.

Still unclear is whether the Belgium-based syndicate was linked to another match-fixing and gambling operation, also involving Armenians, that unraveled in Spain. Spanish police last week announced that 28 professional tennis players, including one who participated in last year's US Open, were linked to that ring, taking bribes to fix results that the group bet on using fake identities.