Riccardo Riccò was hospitalized overnight in an Italian hospital with high fever and apparent kidney failure.

Details were sketchy on exactly what happened or what caused his illness. Doctors at the hospital of Riccò’s hometown of Modena said Monday in an official communique that the Italian rider entered the hospital Sunday evening with high fever and symptoms of kidney failure.

Officials said Monday his condition was “critical, but improving,” with a “reserved” prognosis.

According to reports in the Italian media, Riccò returned Sunday from a five-hour training ride complaining of high fever, as high as 104 degrees. His father transported him to a local hospital, where doctors immediately transferred Riccò to a larger, better-equipped hospital in Modena.

Vacansoleil team manager Daan Luijkx reported in a team statement that Riccò’s condition is improving: “Riccardo had a fever of more than 40C (104F) yesterday, but today he feels much better. The doctors wanted to keep him there for at least one day to have him under observation.”

Later Monday, the Italian news agency ANSA reported that Riccò’s “state of health, critical to start off with, according to the Nuovo Ospedale Civile Sant’Agostino Estense di Baggiovara clinic, has improved.”

Rubinho Ricco, the racer’s father, said he had suffered a “kidney failure” after a Sunday training session amid reports he could be suffering from kidney stones.

He added his son was conscious and talking while the hospital said it would update the racer’s news Tuesday afternoon.

Riccò, 27, was set to start the Tour Mediterranean this week and race the Volta ao Algarve later this month in Portugal as part of his comeback from a racing ban after testing positive for CERA/EPO during the 2008 Tour de France.