Federal prosecutors said Friday that they had closed their investigation of Lance Armstrong without charging him, nearly two years after they began looking into allegations that he and his cycling teammates committed a variety of possible crimes by doping.

The possible crimes being investigated included the defrauding of the government, drug trafficking, money laundering and conspiracy involving Armstrong and other top cyclists. In particular, the authorities were exploring whether money from the United States Postal Service, the primary team sponsor for the first four of Armstrong’s Tour de France wins, was used to buy performance-enhancing drugs.

André Birotte Jr., the United States attorney for the Central District of California, announced the end of the investigation, which involved several federal agencies, in a brief statement. He did not cite a reason for the decision and declined to comment further.