Washington ? A Qatari diplomat was on his way to an official visit with an imprisoned al-Qaida sleeper agent when he touched off a bomb scare by slipping into an airline bathroom for a smoke, officials said Thursday as the diplomat prepared to leave the U.S.

The diplomat, Mohammed Al-Madadi, was going to pay a consular visit to the prisoner, said Alison Bradley, a public relations executive hired to speak for the Qatari Embassy, and a State Department official.

The prisoner, Ali Al-Marri, a citizen of Qatar, is serving eight years after pleading guilty last year to conspiring to support terrorism. Al-Marri was arrested after the Sept. 11, 2001, terrorist attacks, accused of being a sleeper agent researching poisonous gasses and plotting a cyberattack.

Consular officials frequently visit foreigners held in the United States to make sure they are being treated well.

Questions remained about why a diplomat on an official trip, like Al-Madadi, would apparently flout airline security rules. Law enforcement officials said Al-Madadi later joked that he had been trying to light his shoe — an apparent reference to the 2001 so-called shoe bomber, Richard Reid.