Former world champion Tom Boonen of Belgium has been suspended by Quick Step following a positive test for cocaine.
'He is suspended from all activities by the team,' Alessandro Tegner of Quick Step's representative said.
Boonen, who won the Paris-Roubaix classic for the third time last month and is among the top one-day race riders in the world, previously failed a test for cocaine last year.
'The test, which was positive for cocaine, was carried out by the Flemish authorities. It was about two weeks ago,' Mr Tegner said.
Jan Poels, a public prosecutor in the northeast Belgian town of Turnhout, said a search had been carried out at Boonen's home at the end of April in connection with a drugs investigation.
He declined to say whether drugs were found or whether the investigation concerned any particular substance.
Last year, Boonen was withdrawn from Quick Step's Tour de France line-up following a positive test for cocaine.
He apologised and team manager Patrick Lefevere said Quick Step maintained their confidence in him because these were considered private problems.
Last February, a Belgian court found him guilty of cocaine use but decided not to hand down criminal sanctions.
