Possible match-fixing which determined the fate of two top-flight teams is part of a widespread probe into corruption in Belgian football.
Several senior figures have been detained following police raids, with five people charged on Thursday.
Two prominent agents and Club Brugge's Ivan Leko were detained, although the coach was among six later released.
Two games are under suspicion – involving Mechelen, relegated on goal difference, and Eupen, who survived.
Those matches are Eupen's 2-0 defeat by Antwerp on 3 March, part of the penultimate weekend of the regular league season, and Mechelen's 2-0 win over Waasland-Beveren on the final weekend, on 11 March.
Despite Mechelen's victory, they were relegated, while Eupen scored four goals in the last 20 minutes against Royal Excel Mouscron to win 4-0 and survive.
Club Brugge later issued a statement showing their support for their coach, who had "always acted in good faith" and would "give his full co-operation" to the investigation.
The Belgian prosecutor's statement revealed these details:
- Searches were carried out at RSC Anderlecht, Club Brugge, KRC Genk, KV Kortrijk, KV Mechelen, KV Oostende, Sporting Lokeren, AA Ghent and Standard Liege
- In addition, there were searches at the homes of six football club board members, four agents in the football players' market, two referees, one former lawyer, an accountancy bureau, two jewellers, two journalists, a trainer and "some possible accomplices"
- Luxury watches, empty deluxe watch boxes, jewels and cash have been seized
- Agent Dejan Veljkovic, who has been charged, is alleged to have set up financial schemes with clubs – including KV Mechelen, KRC Genk, Sporting Lokeren, Club Brugge and Standard Liege
- Referee Sebastien Delferiere and officials of KV Mechelen and Waasland-Beveren are also among the five people charged
- Mogi Bayat, another agent, is suspected of having manipulated the transfer of various players in order to maximize his own fees at the expense of other parties