WASHINGTON — 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 today as they announced plans to send the diplomat home.

A State Department official and another person close to the matter said 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 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.

No explosives were found on the plane and authorities said they don't think Al-Madadi was trying to hurt anyone during Wednesday's scare.