Tosh Van der Sande has been suspended by Lotto-Soudal after he returned a positive test during the Ghent Six Day in November.
The team say the Belgian returned a positive test for a permitted substance, but they have still taken the decision to suspend him.
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Van der Sande has ridden his entire career for Lotto, joining in 2012.
The rider announced his positive test to the team on Wednesday, when bosses took the decision to suspend him.
According to the team, the unnamed substance occurs in a nasal spray that is permitted providing a rider mentions it during a doping test.
The team is now expecting a UCI investigation.
A statement from Lotto-Soudal, released on Wednesday, said: “Today Lotto-Soudal was notified by its rider Tosh Van der Sande of a positive doping test during the Six Days of Ghent where he took part between November 12 and 18, 2018.
“The substance is a permitted one and occurs in the nasal spray Sofrasolone, that is freely available to be used in competition of mentioned during a control.
“After a meeting with the rider, the board has decided to suspend him, in expectation of the investigation executed by the UCI and to allow the rider to underpin his defence in the best possible way.
“Lotto-Soudal will give no further explanations until the UCI procedure has terminated.”
Van der Sande, 28, has ridden six Grand Tours for Lotto – four times the Vuelta a España and twice the Giro d’Italia.
He rode the Ghent Six Day in November alongside team-mate Jasper De Buyst, the duo finishing in third place.
The event was won by Deceuninck-Quick – Step pairing Elia Viviani and Iljo Keisse.