LOS ANGELES – Federal prosecutors announced Friday that they have closed a two-year inquiry without filing criminal charges in a case that sources said related to doping allegations involving seven-time Tour de France winner Lance Armstrong and his cycling team.

Although the grand jury investigation was confidential, details about various former teammates and associates who were subpoenaed to testify about alleged use of banned substances were widely reported in the media. The allegations roiled the cycling world and threatened to tarnish Armstrong's legacy.

The U.S. attorney's decision to close the case came after blistering criticism from Armstrong's attorneys, who alleged in court papers that government sources had leaked confidential grand jury information "with the transparent agenda of publicly smearing Armstrong and aggrandizing the government's investigation." In a brief statement, U.S. Attorney Andre Birotte Jr. praised the work of investigators but gave no reason for concluding the investigation without charges.

Prosecutors rarely announce the closure of a secret probe, but Birotte said disclosure was warranted because of the "numerous reports about the investigation in media outlets around the world." Armstrong, who has always denied the doping allegations, said in a statement that prosecutors made "the right decision" in dropping the case.

"I commend them for reaching it," he said. "I look forward to continuing my life as a father, a competitor and an advocate in the fight against cancer without this distraction."

Some who had accused Armstrong of doping said closing the case without charges was an injustice.

"This is what happens when you have a lot of money," said Betsy Andreu, who along with her cyclist husband, Frankie, has testified in a separate civil case that she heard Armstrong acknowledge using performance-enhancing drugs.

Despite the end of the criminal probe, the U.S. Anti-Doping Agency said in a statement that it would continue its own investigation into the use of banned substances in cycling.

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

The federal probe had been headed by Food and Drug Administration agent Jeff Novitzky, who previously had led steroid-use inquiries that ensnared baseball's Barry Bonds, Olympic champion Marion Jones and world-champion boxer Shane Mosley, among others.

The grand jury, which began its inquiry around May 2010, heard testimony from a number of Armstrong associates and teammates including former teammate Yaroslav Popovych, exercise physiologist Allen Lim, Olympic medalist Tyler Hamilton and longtime liaison Stephanie McIlvain. The investigation appeared to be spurred by former teammate Floyd Landis, who went public with emails he sent to cycling and anti-doping officials claiming drug use by Armstrong.

Attorneys for Armstrong had asked a federal judge in July to find the government in contempt for leaks to the media.

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