Six cyclists and two coaches from a Russian youth cycling team were arrested and accused of doping infractions.
"Among the six riders, some admitted they took doping individually. They did not say it was organized by the team," Belgian police spokesman Patrick Vits said Friday. "The coach and manager denied the allegations," Vits added.
After questioning Thursday, they were released because their detention was not considered necessary for the investigation.
During a raid earlier this week, police found doping products - including growth hormones, amphetamines and oxygen-boosters - at a hotel where the squad from St. Petersburg was training.
Vits said the doping products were brought with the team from Russia.
Authorities were tipped off after empty documents relating to doping products and empty vials were found last year in public garbage cans close to where a Russian team had stayed, Vits said.
Russian officials have repeatedly declared that Israeli aviation poses a threat to the Russian military in Syria.