Ex-Teammate: I saw Lance Armstrong use EPO

A former teammate of perhaps the world's greatest cyclist, Lance Armstrong, says he used banned performance-enhancing substances with Armstrong to cheat in pro races, including the Tour de France, the sport's ultimate event.

For the first time, former Armstrong teammate Tyler Hamilton reveals details to Scott Pelley never heard in public before of how and when he and some of the former members of the U.S. Postal Service team led by Armstrong used banned substances, including EPO and testosterone, to gain an advantage in races that Armstrong won.

Armstrong on doping claims: Never a failed test

Hamilton's interview is part of a six-month investigation by "60 Minutes" into doping on the cycling circuit and whether Armstrong has used banned substances - which he has steadfastly denied - a matter now under federal investigation.

The Pelley team's report will be broadcast on "60 Minutes" Sunday, May 22 at 7 p.m. ET/PT.

Hamilton, one of Armstrong's closest teammates and a champion cyclist in his own right, has previously denied using banned substances. He came forward to reveal secrets he thought he would harbor for years after he was subpoenaed by the grand jury in the federal investigation and forced to testify. "[Armstrong] took what we all took...the majority of the peloton," Hamilton says, referring to the tight group of bicycles and their riders in a race. "There was EPO...testosterone...a blood transfusion," he tells Pelley.

Hamilton says Armstrong used EPO, a drug that boosted endurance by increasing the amount of red blood cells in his body, to win the 1999 Tour de France, the race he won an astonishing seven times. "I saw [EPO] in his refrigerator...I saw him inject it more than one time like we all did, like I did many, many times."

Another former Armstrong teammate, also a witness in the federal investigation, is Frankie Andreu. He tells Pelley he took banned substances because lesser riders he believed were doping passed him by. "Training alone wasn't doing it and I think that's how...many of the other riders during that era felt, I mean, you kind of didn't have a choice," says Andreu.

The bedrock of Armstrong's denials over the years has been his claim to have never failed one of the hundreds of drug tests he has taken. Hamilton says Armstrong told him he did fail a test in 2001 given during the Tour de Swiss, an important event right before the Tour de France.

That allegation is under investigation by federal authorities.