Federal prosecutors say they are closing a criminal investigation of Lance Armstrong and will not charge him over allegations the seven-time Tour de France winner used performance-enhancing drugs.

In a press release, United States Attorney André Birotte Jr. says the case has been closed but didn't disclose the reason for the decision.

Investigators looked at whether a doping program was created to keep Armstrong and his teammates running at the head of the pack while, at least part of the time, they received government sponsorship from the U.S. Postal Service.

Armstrong won the Tour de France every year from 1999-2005 and has always fiercely denied doping.

Prosecutors, however, began presenting evidence nearly two years ago to a federal grand jury in Los Angeles, and several of Armstrong's former teammates and associates provided testimony.