“The investigation concerns alleged facts of importation of cocaine from South America to Europe, via the port of Antwerp, and its redistribution in Belgium,” prosecutors added in a statement.
No additional information was released right away. Nainggolan, who hails from Antwerp and is now 36, made a comeback last week to play for a lower-tier Belgian team, wrapping up a lengthy career that included 30 appearances and six goals for the national squad.
After stints with Italian clubs like Cagliari, Inter Milan, and Roma, he had been a free agent since last summer until he signed with Lokeren, a team in Belgium's second division.
He kicked off his debut with a goal during Lokeren's 1-1 draw against K. Lierse over the weekend. He had previously returned to Belgium in the summer of 2021 to play for Royal Antwerp but left the club in early 2023.
Known for his tattoos and off-field shenanigans, he faced a suspension earlier this year for using an e-cigarette while sitting on the bench, as reported by Belgian media.