WASHINGTON (AFP) – US air marshals subdued a Qatari diplomat on a flight to Denver in a bomb scare triggered after he reportedly smoked a cigarette and then joked he was trying to ignite his shoes, officials said.

The plane landed safely at Denver International Airport following the disturbance, and US officials later said it appeared the passenger was not trying to blow up the plane, although the incident was under investigation.

But the scare prompted fighter jets to scramble and intercept the flight amid fears of a possible repeat of a passenger’s foiled attempt to bring down a Northwest Airlines jet on Christmas Day as it approached to land at Detroit.

“The president was briefed by National Security Advisor General Jim Jones and National Security Staff Chief of Staff Denis McDonough at 8:50 pm EDT and appropriate actions were taken to ensure the safety of the traveling public,” a White official said.

“The incident is currently under investigation,” the official added.

Obama was aboard Air Force One at the time, enroute to Prague to sign a nuclear arms reduction treaty with Russia.

Qatar’s ambassador to Washington Ali Bin Fajad al-Hajari said in a statement that the diplomat was traveling to Denver on official embassy business.

“He was certainly not engaged in any threatening activity,” the ambassador said. “The facts will reveal that this was a mistake, and we urge all concerned parties to avoid reckless judgments or speculation.”

Law enforcement authorities initially notified key lawmakers that US air marshals subdued the Qatari national, who had apparently sought to “ignite their (his) shoe” on the flight, a congressional aide told AFP on condition of anonymity.

“Air marshals jumped in, and the cockpit wasn’t breached,” the official said.

The man was identified in US media reports as Qatari diplomat Mohammed al-Modadi, 27, who as the third secretary and vice consul of the Qatari embassy in Washington enjoys full diplomatic immunity.

The FBI was investigating the incident, but a US official told AFP the incident was “not what it appeared to be” and there was no attempt to detonate a bomb.

NBC News reported the man had simply said he was putting out a cigarette he had smoked in the restroom on the sole of his shoe. Smoking is prohibited on all US passenger flights.

ABC News said the diplomat told marshals “I’m lighting my shoes on fire.”

A US security official acknowledged “it may have been a massive misunderstanding,” telling ABC that Al-Modadi may have been making a “sarcastic” comment when he was confronted by two air marshals.

NBC News said a search of the man found no explosives and that bomb-sniffing dogs found no traces of explosives aboard the aircraft.

The Transportation Security Administration (TSA) said the passenger was placed in custody, adding it was “monitoring” the incident.

Federal officials told NBC the incident occurred half an hour before United Airlines flight 663 was due to make a scheduled stop in Denver on a flight that originated at Washington’s Reagan National Airport.

A flight attendant smelled smoke as a passenger came out of a restroom, and alerted an air marshal, the report said.

The marshal confronted the man, and then wrestled him to the ground after he made the statement about lighting his shoes, NBC said.

The pilot declared an emergency, and two F-16 fighter jets raced to intercept the aircraft around 6:45 pm (0045 GMT Thursday) under the authority of the North American Aerospace Defense Command (NORAD).

“Shortly before landing in Denver, a passenger possibly caused a disturbance on the plane. Upon intercepting the aircraft, the F-16s escorted the aircraft until it landed safely without incident at approximately 6:50 pm (0050 GMT) where the plane was met by local law enforcement,” NORAD said.

The plane was carrying 157 passengers and six crew members on a flight originally scheduled to ultimately arrive in Las Vegas after a scheduled stop in Denver.

The incident came a week after the United States unveiled new security measures subjecting all US-bound plane passengers to screening methods that use real-time intelligence to target potential threats, replacing the mandatory screening of passengers from a blacklist of 14 mainly Muslim countries.

The measures were announced in the wake of a Nigerian man’s failed attempt to detonate explosives concealed in his underwear on a Detroit-bound flight from Amsterdam on Christmas Day.