Another ex-teammate says Armstrong used EPO

Accusations that the world's best-known cyclist, Lance Armstrong, cheated by taking performance-enhancing drugs have been made in a "60 Minutes" interview with former teammate Tyler Hamilton, who admitted he took those drugs as well.

Excerpts from the interview, which will be featured on Sunday's broadcast, were released Thursday. On Friday, Hamilton surrendered the gold medal he won in the 2004 Olympics.

Now "60 Minutes" is reporting Hamilton is not the only former teammate to claim he saw Armstrong doping.

Cyclist Hamilton hands over Olympic gold medal

CBS News chief investigative correspondent Armen Keteyian reports that, like his signature move in the mountains, Armstrong went on the attack Friday. As he has repeatedly done in the past, he targeted the credibility of those who accuse him of using illegal performance-enhancing drugs.

The current target: Hamilton. He told "60 Minutes" correspondent Scott Pelley about his -- and Armstrong's -- repeated use of banned substances, including the blood-boosting drug EPO.

"You saw Lance Armstrong inject EPO?" Pelly asked Hamilton.

"Yeah, like, we all did like I did many, many times," Hamilton said.

On his website, facts4lance.com, Armstrong tore into Hamilton, calling him "a confessed liar in search of a book deal."

But it turns out the six-month "60 Minutes" investigation into Armstrong is anchored in far more than the on-camera accounts of Hamilton and another former U.S. Postal teammate, Frankie Andreu.

Instead, this Sunday's report breaks major new ground based on evidence tied to an ongoing federal grand jury investigation of Armstrong in Los Angeles.

It appears the federal investigation, with its subpoenas and sworn grand jury testimony, has broken cycling's code of silence, Pelley reports. It's not known how many U.S. Postal riders were using performance-enhancing drugs, but "60 Minutes" has learned at least three have told federal authorities they used banned substances and witnessed Armstrong using them too.

One of those riders is Armstrong's other close teammate, George Hincapie. The broadcast has been told that now, for the first time, Hincapie has testified to federal investigators that he and Armstrong supplied each other with the blood-booster EPO and discussed having used testosterone, another banned substance, during their preparation for races.

Through his attorney, Hincapie declined to be interviewed, citing the ongoing investigation.

When it comes to such an investigation, sworn testimony from Hincapie is a game-changer. Quiet, untouched by scandal, he is the only rider to be at Armstrong's side for all seven of his record Tour de France victories. If anyone would know if Armstrong was doping, it would be Hincapie.

This federal investigation goes back to last August. It could end as early as next month. But what's interesting is that the federal investigator involved is the same one behind the probe of the Bay Area Laboratory Co-Operative steroids ring, known as BALCO, which allegedly has ties to Barry Bonds.