Justice Department prosecutors announced today that they are closing their exhaustive criminal investigation of 7-time Tour de France winner Lance Armstrong without filing charges.

The government was investigating Armstrong not simply for doping, as three former teammates on the Texan’s Tour de France cycling teams alleged. Prosecutors had been trying to determine if Armstrong and other team members violated federal conspiracy, fraud or racketeering charges. The alleged doping was part of a larger case that Armstrong defrauded the US Postal Service, which sponsored his cycling team from 1999 through 2004, by competing with the aid of prohibited performance-enhancing drugs. While government investigators needed to prove that Armstrong and his teammates doped, the legal focus of the potential criminal case was that doping was carried out on a team wide scale that as a result violated the contract they had with US Postal Service as a title sponsor -- and therefore represented an instance of fraud against the federal government.

At the culmination of a full-court-press investigation led by famed sports drug cheat investigator Jeff Novitsky, Los Angeles-based United States Attorney André Birotte Jr. said in a press release said that Armstrong will not be charged but offered no reasons for the decision.

Prosecutors called multiple witnesses to a federal grand jury in Los Angeles in the last year, but apparently felt they lacked proof to bring charges.

Armstrong, who had been accused of using performance enhancing drugs by teammates Frankie Andreu, Floyd Landis and Tyler Hamilton, often pointed out that he never failed a drug test. Armstrong released a statement today saying he was “gratified.” He added, “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.”

Landis, who was found guilty of doping in the 2006 Tour de France and was stripped of his title, made several claims against Armstrong last year. Last May, Olympic champion Tyler Hamilton, who was banned from cycling after testing positive twice for doping, told CBS’s “60 Minutes” that he saw Armstrong using EPO in 1999, the year of his first Tour de France victory. Hamilton told the prime time CBS news program “"I saw him inject it more than one time like we all did, like I did many, many times." Hamilton added: "Armstrong took what we all took -- the majority of the peloton took. There was EPO, testosterone, blood transfusions."

In response to the allegations made on “60 Minutes” Armstrong wrote on his Twitter account: "I have had a 20-year career, 500 drug controls worldwide, in and out of competition, and never a failed test. I rest my case."

As reported in Velo News, U.S. Anti-Doping Agency CEO Travis Tygart said in a statement that his organization would pursue documents from the investigation.

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

With the federal case dropped, Armstrong remains free to pursue further endurance challenges in triathlon, off road cycling and running - barring further action by USADA.