(CNN) -- Riccardo Ricco has been suspended by his Dutch-based Vacansoleil cycling team amid claims that the Italian gave himself a blood transfusion.
Ricco -- who only returned to the sport last March after being handed a 20-month ban for doping during the 2008 Tour de France -- was admitted to a hospital in Modena on Sunday.
His father told reporters at the time that Ricco had been suffering from a high fever and suspected kidney failure.
But Italian media claimed the 27-year-old had admitted to doctors that he had made himself ill by injecting contaminated blood.
And now his team have issued an official statement, saying they have found enough proof of a doping infraction to suspend the rider with immediate effect.
The statement said: "Internal research results following the illness and rumors regarding Ricco have given the team sufficient reason to suspend the Italian with immediate effect."
It continued: "Last Tuesday, the team started an urgent investigation following the hospitalisation of Riccardo Ricco. Three days later the results of this study brought the team to the conclusion that an immediate suspension of Ricco was required.
"The violation of internal regulations of the team and other indications justify this measure. The team cannot prejudge but emphasises that a zero-tolerance policy towards doping is practised."
Blood doping -- an action that increases the amount of red blood cells available to carry oxygen to the muscles -- has been a problem in cycling for a number of years, with disgraced 2006 Tour de France winner Floyd Landis admitting last year that he blood-doped during his career.
Blood cells are not damaged by freezing, consequently a "blood doper" can remove blood from their body, safely store it, and re-inject it when increased aerobic capacity and stamina is needed.
However, if the blood is stored incorrectly, it can become infected, resulting in severe illness if transfused.
The practice of blood doping is banned by all official sporting governing bodies and Ricco now faces expulsion from competitive cycling if found guilty, as well as a possible jail sentence in a country where all forms of doping are classed as illegal.
Ricco has yet to react to the claims surrounding his hospital stay.