A Qatari diplomat was on his way to meet an imprisoned al-Qaida agent when he touched off a bomb scare by slipping into an airline bathroom for a smoke, officials said Thursday as they announced plans to send the diplomat home.

A State Department official and another person close to the matter say Mohammed Al-Madadi was going to meet Ali Al-Marri in prison. Consular officials frequently visit foreigners held in the United States to make sure they are being treated well.

Al-Marri, a citizen of Qatar, is serving eight years in prison after pleading guilty last year to conspiring to support terrorism. He was arrested after the Sept. 11, 2001 terrorist attacks, accusing him of being a sleeper agent researching poisonous gases and plotting a cyberattack.

The visit with such a high-profile prisoner suggests that Al-Madadi would have been very aware of terrorism concerns when he sneaked into the plane's bathroom for a smoke and, according to authorities, joked about lighting his shoe on fire.

The people who discussed the case did so on condition of anonymity because they were not authorized to discuss the matter.

No explosives were found on the plane and authorities said they don't think Al-Madidi was trying to hurt anyone during Wednesday's scare. He enjoys diplomatic immunity from U.S. prosecution and will not be criminally charged, authorities said. The State Department official said Qatar had not yet informed the administration how they will handle the case.

Wednesday's scare came three months after the attempted terror attack on Christmas Day when a Nigerian man allegedly tried to blow up a Detroit-bound airliner. The Nigerian, Umar Farouk Abdulmutallab, went to the bathroom just before he allegedly tried to ignite his bomb in his seat. Since then, law enforcement, flight crews and passengers have been on high alert for suspicious activity on airplanes. That scare exposed major holes in the country's national security and prompted immediate changes in terror-screening policies.

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Associated Press writer Matt Apuzzo contributed to this report. Banda contributed from Denver.