French doctors say they tested Armstrong's hair, urine and blood March 17. They say they found no traces of drugs.
However, the agency, known as AFLD, said in a statement Thursday that a doctor charged with testing Armstrong last month claimed Armstrong "did not respect the obligation to remain under the direct and permanent observation" of the tester.
The AFLD says it is can impose sanctions on the American rider, but didn't indicate what they would be.
Armstrong is in training to ride in this year's Tour.
