Top clubs, agents and referees were targets of police raids on Wednesday, the federal prosecutor’s office has confirmed.
The investigation began at the end of 2017 following a report by the police's sport fraud unit after there was an indication of "suspicious" transactions in professional Belgian football.
During their investigation, the authorities concluded there was evidence of the "influencing of competitions in the 2017-18 season", using this to expand the probe to include a look into match-fixing.
Among the premises searched were the offices of top-tier clubs Anderlecht and Club Brugge, who are competing in this season’s Champions League.
The prosecutor's office confirmed the raids in a statement, which read: "The judicial investigation concerns activities in the framework of a criminal organisation, money laundering and private corruption.
"The house searches this morning [Wednesday] were conducted at several football clubs active within the Jupiler Pro League. Various documents and files were seized.
"We also carried out house searches of board members of football clubs, players' agents, referees, a former lawyer, an accounting firm, a jeweller, journalists and a number of possible accomplices.
"A large number of people were deprived of their freedom and taken away for thorough interrogation.
"The house searches abroad mainly took place at the houses of foreign legal entities that would be used to set up the suspicious financial transactions. Documents and funds were seized from bank accounts and in safes."
Anderlecht confirmed they are working with police, with their dealings with unnamed player agents investigated.
"Today [Wednesday], the federal police conducted a search at RSC Anderlecht," the club said in a statement.
"This action is part of a judicial inquiry into the practices of certain players' agents. The club is co-operating fully with the investigation and will make no further comments."
Brugge chairman Bart Verhaeghe confirmed his club are also being investigated, though he is confident they have nothing to hide.
"Of course, we co-operate positively and constructively," he is quoted as saying by HLN. "The investigators want to see contracts and invoices, which we have given, which will show that everything is clean and in order."
Standard Liege and Lokeren also confirmed they are co-operating with police after their offices were raided on Wednesday.