Image 1 of 3 Shades of Paris 2005. Lance Armstrong (RadioShack) addresses the crowd. (Image credit: Bettini Photo) Image 2 of 3 Lance Armstrong rocked up and won (Image credit: Trent Bona Photography) Image 3 of 3 Gone for good? Lance Armstrong (RadioShack) made his final international appearance. (Image credit: Bettini Photo)

US radio station National Public Radio (NPR) has raised concerns over the decision that saw the United States Attorney's Office in Los Angeles close down a two-year investigation into allegations of fraud and doping that involved the US Postal Service Team and Lance Armstrong. Armstrong has denied ever taking performance enhancing and welcomed the decision to close the case. He may still face investigation from USADA.

NPR has alleged that sources in the FBI, FDA and US Postal Service were ‘shocked, surprised and angered’ and that federal authorities only had 30 minutes notice before the United States Attorney's Office released a press release to the media on Friday afternoon.

According the NPR, sources indicated that charges were close to being brought against a number of individuals, which included fraud, witness tampering, mail fraud, and drug distribution. One source, NPR says, said there were ‘no weaknesses in the case’.

However, NPR also adds that a person with knowledge of the decision said that US Attorney didn’t agree that there was sufficient evidence of crimes.

Cyclingnews spoke to a source who had co-operated with the federal investigation. The source indicated that the NPR reports held weight.

“I talked to someone within the investigation but the reason why the case was shut down was due to a one-man decision. The evidence against those involved was absolutely overwhelming. They were going to be charged with a slew of crimes but for reasons unexplained he closed the case saying it wasn't open for discussion,” the source said.

A press release from United States Attorney Andre Birotte Jr. stated his office was "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 stated: “I am gratified to learn that the U.S. Attorney's Office is closing its investigation," Lance 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."

Cyclingnews attempted to contact federal investigators and Armstrong's attorney for comment.