LOS ANGELES – Federal prosecutors dropped their investigation of Lance Armstrong on Friday, ending a nearly two-year effort aimed at determining whether the seven-time Tour de France winner and his teammates participated in a doping program.

Armstrong has steadfastly denied he doped during his unparalleled career, but the possibility of criminal charges threatened to stain his legacy as the world’s greatest cyclist and could have cast a shadow over his cancer charity work.

“I am gratified to learn that the U.S. Attorney’s Office is closing its investigation,” Armstrong said in a statement. “It is the right decision and I commend them for reaching it. I look forward to continuing my life as a father, a competitor, and an advocate in the fight against cancer without this distraction.”

The probe, anchored in Los Angeles where a grand jury was presented evidence by federal prosecutors and heard testimony from Armstrong’s former teammates and associates, began with a separate investigation of Rock Racing, a cycling team owned by fashion entrepreneur Michael Ball.

U.S. Attorney André Birotte Jr. announced in a press release that his office “is closing an investigation into allegations of federal criminal conduct by members and associates of a professional bicycle racing team owned in part by Lance Armstrong.”

Armstrong won the Tour de France every year from 1999 to 2005.

Betsy Andreu, who with her husband and former Armstrong teammate, Frank, accused the cycling champion of doping, said she was shocked by Birotte’s decision.

“Our legal system failed us,” she said. “This is what happens when you have a lot of money and you can buy attorneys who have people in high places in the Department of Justice.”

The case also was spurred by disgraced cyclist Floyd Landis, who claims Armstrong had a long-running doping system in place while they were teammates.

Landis was stripped of the 2006 Tour de France title for drug use. One of the most serious accusations came during a “60 Minutes” interview last May when former teammate Tyler Hamilton said he saw Armstrong use EPO during the 1999 Tour de France and in preparation for the 2000 and 2001 tours.

U.S. anti-doping officials said Friday they will not be dissuaded by the government’s decision to close the Armstrong probe.

“Unlike the U.S. Attorney, USADA’s job is to protect clean sport rather than enforce specific criminal laws,” said Travis Tygart, chief executive officer of the U.S. Anti-Doping Agency. “Our investigation into doping in the sport of cycling is continuing and we look forward to obtaining the information developed during the federal investigation.”