Di Luca wore the pink jersey on eight stages of this year's Giro
Giro d'Italia runner-up Danilo Di Luca has been provisionally suspended after testing positive for the banned blood booster Cera.
The 33-year-old LPR rider won two stages in this year's Tour of Italy and wore the pink jersey as race leader.
"The decision was made in response to a report to blood samples collected during the Giro on 20 and 28 May 2009," said the International Cycling Union.
The 2007 Giro winner faces a two-year ban if his B sample returns positive.
Di Luca served a three-month suspension in late 2007 after the Italian Olympic Committee (CONI) found him guilty of frequenting a doctor accused of supplying doping products to athletes.
Last year CONI tried to ban him for two years for having abnormal hormone levels during the 2007 Giro but after much legal wrangling he was found not guilty because of insufficient evidence.
Di Luca, who finished the Giro 41 seconds behind Denis Menchov, is not competing in the Tour de France.