Warsaw - All 160 players tested ahead of Euro 2012 as part of an anti-doping programme returned negative samples, European football's organising body UEFA said on Sunday.
Ten players from each of the 16 teams were tested in pre-competition tests, in which blood and urine samples were taken.
"In addition, the haematological and hormonal profiles from the analysis conducted in all the samples show that there is absolutely no prevalence of blood or hormonal manipulation among players participating in the competition," UEFA said.
During the tournament, all 31 matches will be subject to controls, with four samples after each match taken by UEFA's doping control officers. Unscheduled tests will also take place in rest periods between matches.
Samples are being analysed by Warsaw's Institute of Sport laboratory, which is accredited to the World Anti-Doping Agency (WADA).
Pre-competition tests carried out before Euro 2008 in Switzerland and Austria returned similar results as this year.