Belgian authorities charged five people on Thursday in relation to a fraud and possible match-fixing probe relating to the country's top division.
Four were charged with belonging to a criminal organisation and corruption, while a fifth person was charged with money laundering. Prosecutors said match-fixing allegations centered on the relegation battle from the top division last season and did not involve a major club.
Ivan Leko, the coach of Belgian champions Club Brugge, spoke to investigators along with agents Mogi Bayat and Dejan Veljkovic on Thursday.
The year-long probe relates to suspect financial operations by sports agents on transfers, including tax evasion, money laundering and private corruption. During the probe, investigators said they also found indications of match-fixing during last season's relegation battle.
Belgium and Manchester City defender Vincent Kompany said he was not surprised by the developments because the sector has too long been veiled in secrecy instead of openness.
"The thing I don't get is that, internationally, it has not yet become totally transparent," Kompany told VTM network.
"If you talk about the soccer sector, you cannot be surprised. The link with human trafficking, the drug trade and prostitution, where a lot of money goes around, is very close."
The scandal was revealed publicly on Wednesday when authorities carried out 57 police raids in Belgium and around Europe. In all, 44 raids were staged in Belgium and 13 more in France, Luxembourg, Cyprus, Montenegro, Serbia and Macedonia.
Mogi Bayat, a high profile figure who has brokered a series of player transfers in the country, faced questions on Thursday morning, his lawyer said.
The lawyer of former Anderlecht general manager Herman Van Holsbeeck told broadcaster RTL his client had been released on Wednesday after giving information about transfers and contracts.
Part of the investigation has focused on an extraordinary end to the regular season in Belgium's top division in 2017-18. Mechelen were relegated on goal difference after they won their final match 2-0, while Eupen scored four goals in the last 20 minutes against Royal Excel Mouscron to win 4-0 and survive relegation.
Information from Reuters was also used in this report.