US media are reporting that cyclist Lance Armstrong is facing a fresh federal investigation after admissions he took performance-enhancing drugs.

Attorney Andre Birotte, who oversaw an earlier inquiry, had said aprevious decision not to prosecute still stood.

However, ABC News reported  that: "Agents are actively investigating Armstrong for obstruction, witness tampering and intimidation".

It added that Birotte "does not speak for the federal government as a whole".

Armstrong confessed to taking performance-enhancing drugs during all seven of his Tour de France wins in an interview with Oprah Winfrey last month.