Lance Armstrong is facing new drug allegations.

In a 60 Minutes interview airing Sunday, former cycling teammate Tyler Hamilton claims that he witnessed the seven-time Tour De France champ using the performance enhancing drug EPO while prepping for the race in 1999, 2000 and 2001.

PHOTOS: Remember these celeb scandals

"I saw it in his refrigerator and I saw him inject it more than one time, like we all did many, many times," said Hamilton of the substance which helps boost endurance.

PHOTOS: See Armstrong's BFF and other star bromances

For his part, Armstrong, 39, took to Twitter to refute the charges. "20+ year career. 500 drug controls worldwide, in and out of competition. Never a failed test. I rest my case," he tweeted Thursday, May 19.

PHOTOS: Celeb dads

Hamilton's accusations come one year after Floyd Landis admitted to doping and claimed that Armstrong and other teammates also used performance enhancing drugs.

Watch Hamilton's interview, a part of a six-month investigation by 60 Minutes on doping in the cycling circuit, on CBS this Sunday.

Get more Us! Follow us on Twitter, Friend us on Facebook, Subscribe to Us Weekly