Boonen with his Paris-Roubaix trophy in April [AFP]

Belgian Boonen failed an out-of-competition test for the illegal recreational drug and has been suspended by his team Quick Step.

The rider, who won the Paris-Roubaix classic for the third time last month and is among the top one-day racers in the world, was spared by a Belgian court in February after being found guilty of using cocaine in May last year.

"The test, which was positive for cocaine, was carried out by the Flemish authorities," team spokesman Alessandro Tegner said on Saturday.

"It was about two weeks ago."

In a statement, Quick Step added: "The staff are working closely with team sponsors and will continue to update the situation during the weekend evaluating eventual further action."

'Drugs search'

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Last year, Boonen was withdrawn from Quick Step's Tour de France line-up following his positive test for cocaine.

He apologised and team manager Patrick Lefevere said Quick Step maintained their confidence in him because the matter was considered a private problem.

Boonen, who became world champion in 2005, could now face possible criminal charges carrying a jail sentence of between three months and five years.

The 28-year-old Belgian was supposed to ride in the Tour of Catalunya at the end of the month before taking part in the Dauphine Libere in June in order to prepare for the Tour de France.

Tour organisers Amaury Sport Organisation (ASO) and the International Cycling Union (UCI) were not immediately available for comment.