(CBS/AP) PARIS - The head of the U.S. Anti-Doping Agency tightened security at his organization after receiving several death threats during his investigation of Lance Armstrong.
"The Armstrong affair has prompted death threats against me. I received three of them, individual initiatives, in my opinion. Once again, the FBI dealt with that," Travis Tygart said in an interview published Monday in French sports daily L'Equipe from USADA offices in Colorado Springs, Colo.
"The BALCO case changed everything; we received death threats for the first time," he added. "Two for Terry Madden, my predecessor. One for me and my family later when the (Floyd) Landis confessions first came out."
In August, Armstrong dropped any further challenges to USADA's allegations that he took performance-enhancing drugs to win the Tour de France from 1999-2005. A day later, USADA stripped Armstrong of his Tour titles and banned him for life. Armstrong, who has always denied doping and points to hundreds of tests that he has passed, has claimed Tygart has a vendetta against him.
"I accept being accused, mistreated. That's me, the public face of USADA. Am I a target? I won't shirk my responsibility," Tygart said. "The most important thing is to protect my team. And to maintain the respect of the athletes who don't cheat."
The International Cycling Union has yet to ratify USADA's decision to strip Armstrong, saying it needs to see evidence first. Tygart said USADA would provide the files to the UCI by the end of the month.
He said USADA was entitled to act beyond the eight-year statute of limitations normally applicable within the framework of the World Anti-Doping Code.
"This right no longer exists once the prosecution manages to prove that the athlete who cheated influenced the witnesses who could have proved his guilt during these years," Tygart said. "We are certain that this happened (with Armstrong), and we will explain this to the UCI when we give them the file."
Tygart also said that Armstrong could be called to testify against Johan Bruyneel, his former team manager at Postal during the years he dominated the Tour. Bruyneel has chosen to turn to USADA's Anti-Doping Review Board and be heard before their panel.
"I don't know what Bruyneel is hoping for. He has everything to lose," Tygart said. "Playing for time? Profiting from the inertia of the system? He will be heard before the end of the year. Lance Armstrong could be heard as a witness, under oath, like the others.
"There's no safety net in this game. If there's perjury, that's serious."
In all, USADA said up to 10 former Armstrong teammates were set to testify against him. Included in the case were e-mails sent by Floyd Landis, who was stripped of the 2006 Tour de France title for doping, describing an elaborate doping program on Armstrong's Postal Service teams, and Hamilton's interview with "60 Minutes" claiming had personal knowledge of Armstrong doping. (Watch interview below).