The British Team Sky rider had twice the permitted level of legal asthma drug Salbutamol in his body.
The UCI has asked Froome to provide more information but has not suspended him.
Team Sky said the 32-year-old rider had suffered from asthma since childhood and had been affected by symptoms during the Vuelta a Espana, the Tour of Spain, which he went on to win.
But the team said he had taken no more than the allowable amount of Salbutamol.
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The team said Froome had declared his use of the medication, adding: "The notification of the test finding does not mean that any rule has been broken."
Froome said the UCI was "absolutely right" to scrutinise the test results.
He said that during the race he had "followed the team doctor's advice to increase my Salbutamol dosage".
"Together with the team, I will provide whatever information it requires," he added.
Froome was notified of the test on September 20, the day he finished third in the world time-trial championship in Bergen, Norway.
He has not competed since then, but has announced his intention to try to win the three big tours, in France, Spain and Italy, in 2018.
The test will raise new questions about British cycling following the scandal surrounding the only previous British Tour de France winner, Bradley Wiggins, over his use of so- called therapeutic use exemptions (TUEs).
Wiggins and Sky have repeatedly denied any wrongdoing, saying the drug was prescribed to treat a longstanding pollen allergy.
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