Valverde won the opening stage of the 2008 Tour de France
Spanish cyclist Alejandro Valverde has been put under investigation by Italian police as part of an anti-doping probe.
Investigators want to know if blood samples he gave when the Tour de France crossed over into Italy last year match anonymous DNA from a Spanish inquiry.
Spain launched Operation Puerto in 2006 after raids at addresses in Madrid and Zaragoza uncovered doping paraphenalia.
Valverde was summoned to Italy to discuss the possible violations, which the Caisse D'Epargne rider denies.
Last year a Spanish court closed the Puerto investigation into a blood doping ring after concluding that no criminal offences had been committed, although Spanish media last month reported it could be reopened.
On Wednesday a Madrid judge refused to hand over a blood sample the Italian Olympic Committee (CONI) wanted to test, saying the Italian body did not have the required judicial mandate to investigate.
CONI said the refusal would not hamper their case.
Valverde, who topped the world rankings last year, took part in the 2007 World Championships despite world governing body the International Cycling Union (UCI) trying to prevent his participation because of his links to the Puerto affair.
If found guilty of a doping offence, the 28-year-old could face a two-year ban.