Spanish cyclist Iban Mayo has not breached any doping rules.
Italian riders Alessandro Petacchi and Leonardo Piepoli, however, remain under scrutiny for their doping tests from the Italian tour.
The Gazzetta dello Sport had reported that an abnormal level of testosterone was found in Mayo's system in a doping control during the Giro.
"No breach of the UCI anti-doping rules was committed by the Spanish rider Iban Mayo of the Saunier Duval team," cycling's governing body said in a statement, adding that it "regretted the premature publication of this news."
"The history of this particular case shows the vital need to await the closure of the relevant investigations before reaching conclusions," the UCI said.
The Gazzetta also reported that high levels of salbutamol, a substance normally used to treat asthma, were found in Petacchi and Piepoli.
"In the other cases, the analyses requested by the UCI are still in progress," the UCI said.
Petacchi won five stages in the race - which ended June 3 - and Piepoli and Mayo won one stage each. None of the riders finished in the top 10 overall.
Spanish broadcaster EiTB said Mayo is known to have a naturally occurring high level of testosterone.
Andrea Agostini, a spokesman for Petacchi's Milram team, said the rider has a certificate from the UCI that allows him to take asthma medication.
Agostini said his team has not received any official notification of an adverse result from the UCI.
"Right now we're talking about nothing," Agostini said.
Milram said in a statement that it contacted the UCI on Thursday in response to the reports and the UCI said that further exams on Petacchi's samples are underway at a lab in Barcelona.
Piepoli also reportedly has a medical certificate authorizing use of anti-asthma drugs.
Petacchi's five stage wins in this year's race gave him 24 for his Giro career. He also won the points jersey awarded to the top sprinter.
Piepoli won the mountainous 10th stage and took the jersey for best climber. He also was the catalyst for mountain victories by teammates Riccardo Ricco and Gilberto Simoni.
Mayo won the 19th stage in a solo breakaway.
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