It's alleged dozens of suspect deliveries of medicines based on ephedrine occurred in 2007/8. Ephedrine is an innocuous substance used in cough mixture, but can be employed to manufacture crystal meths.
The ephedrine was bound for Mexican drugs baron Ezio Figueroa Vazquez, who was able to produce 70 million drug tablets with a street value of 360 million euros.
The Belgian drug companies based in Brussels and West Flanders deny any involvement. They say that they were unaware of the final destination and were duped by a go-between.
Prosecutors are unconvinced and point to evidence from emails and telephone traffic.