International Olympic and anti-doping officials say they are implementing the toughest drug-testing program in Winter Games history, using intelligence to target athletes and events considered most at risk.

Authorities say they are focusing their efforts on weeding out dopers through rigorous pre-games and pre-competition tests. Armed with an improved scientific method that can detect drug use going back months rather than days, the International Olympic Committee will conduct a record number of tests.

Urine and blood samples will be stored for eight years for retroactive testing, providing further deterrence to anyone thinking they can avoid being caught, Olympic officials said.