PARIS -- Chris Froome failed a doping test during the Spanish Vuelta in September and is facing a suspension from cycling ahead of his attempt to win a record-equaling fifth Tour de France title next year.

Froome won his fourth Tour title this year and followed it with a victory at the Vuelta. But Team Sky said Wednesday that Froome, who has not been suspended, had a concentration of asthma drug salbutamol two times higher than the World Anti-Doping Agency's permitted levels.

"Analysis indicated the presence of salbutamol at a concentration of 2,000 nanograms per milliliter (ng/ml), compared with the WADA threshold of 1,000 ng/ml," Team Sky said.

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Team Sky said it has been informed by the International Cycling Union (UCI) that the urine test was taken on Sept. 7, during the three-week Spanish Vuelta.

Froome said the UCI has asked him to provide information about the failed test, which was taken after Stage 18.

The Briton, 32, said he increased his dosage of the drugs but stayed within the legal limits. He added the UCI is "absolutely right" to ask questions, according to BBC News.

Tour de France winner Britain's Chris Froome, wearing the overall leader's yellow jersey, second place Rigoberto Uran of Colombia, left, and third place Romain Bardet of France, right, celebrate on the podium after the twenty-first and last stage of the Tour de France cycling race over 103 kilometers (64 miles) with start in Montgeron and finish in Paris, France, Sunday, July 23, 2017. Franck Faugere / AP

Froome's use of asthma medication has been well documented, and the Kenyan-born rider has often been spotted using inhalers in the peloton. He has repeatedly faced questions on whether he is a clean rider, especially during the Tour de France, and has always denied wrongdoing.

Salbutamol is a drug that helps expand lung capacity and can be used as a performance-enhancing drug to increase endurance. Commonly marketed as Ventolin, salbutamol is classified as a beta-2 agonist and WADA allows it to be taken through inhalation only, in limited amounts.

Sky said Froome had to take an increased dosage of salbutamol without exceeding the permissible dose after he "experienced acute asthma symptoms" during the final week of the Vuelta.

If found guilty of doping, Froome could lose his Vuelta title and be suspended for a long period. Sprinter Alessandro Petacchi was suspended for one year for testing positive for salbutamol during the 2007 Giro d'Italia.

Vuelta organizers said they are waiting for "official conclusions" from the UCI about the case.

"The position of La Vuelta's organizer is one of extreme caution, as it hopes for this issue to be resolved as quickly as possible," they said in a statement.

Froome was expected to attempt to join cycling greats Eddy Merckx, Bernard Hinault and Miguel Indurain on the list of five-time Tour de France champions in July. Lance Armstrong won seven titles, but all of them were stripped because of doping.

Team Sky has been dominating the field at the Tour de France in recent years, but has been targeted by doping accusations. Britain's anti-doping agency last month closed an investigation into the team without bringing charges. The case centered on the contents of a medical package dispatched to former Tour champion Bradley Wiggins at a key pre-Tour race in 2011.

Team Sky was established in 2009 by Dave Brailsford, the man behind Britain's 14 medals at the 2008 Beijing Olympics, with the target of producing the country's first Tour champion -- a feat accomplished by Wiggins in 2012. Froome, his former teammate, has taken over since as Britain's most successful road rider.

After successfully defending his Tour de France title in July, Froome went on to win the Spanish Vuelta for the first time.

"My asthma got worse at the Vuelta so I followed the team doctor's advice to increase my Salbutamol dosage," Froome said. "As always, I took the greatest care to ensure that I did not use more than the permissible dose. I take my leadership position in my sport very seriously. The UCI is absolutely right to examine test results and, together with the team, I will provide whatever information it requires."

The UCI said in a statement that Froome's "B'' sample confirmed the result, but stressed that "the presence of a specified substance such as salbutamol in a sample does not result in the imposition of such mandatory provisional suspension against the rider."

Sky stressed the abnormal result does not mean Froome has breached anti-doping rules and Brailsford insisted he has the "utmost confidence that Chris followed the medical guidance in managing his asthma symptoms, staying within the permissible dose for Salbutamol."

According to Swiss physiologist Raphael Faiss, intense effort, fatigue and dehydration can affect urine concentrations of salbutamol in doping tests.

Quoting a scientific study from 2015, Faiss, a researcher in anti-doping at Lausanne University, told The Associated Press in a telephone interview that "between 10 and 30 percent" of the people tested may have readings beyond the permitted thresholds when inhaling the legal quantity of salbutamol.

Froome said last month that he wants to ride in next year's Giro d'Italia in an attempt to win his third Grand Tour in a row. A victory at the Italian race would make him the seventh rider to win all three Grand Tours, and only the third to hold the three titles at the same time.