WASHINGTON — A Saudi immigrant suspected of once applying to join Al Qaeda’s most notorious training camp was arrested on a charge of visa fraud in Oklahoma, where he had been living for years with his family, federal law enforcement officials said on Tuesday.

The F.B.I. discovered the man, Naif Abdulaziz Alfallaj, only recently, when the authorities matched his fingerprints to those taken from a document captured in Afghanistan, the officials said. The document was an application for the Farooq camp, where four of the Sept. 11 hijackers trained.

He apparently filled out the application in 2000, when he was about 17, the officials said, well after Al Qaeda had made its intentions of attacking the United States and its allies known to the world. Anyone who tried to join the camp would have known that Al Qaeda was a terrorist organization, the law enforcement officials said.

Typically people who applied to the camp filled out what was known as a “mujahedeen data form.” They needed an invitation to join the camp and a reference from someone known and trusted by Al Qaeda. Trainees learned how to use weapons and explosives at the camp. After training, camp attendees fought with Al Qaeda or the Taliban in Afghanistan.

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