The official said FBI agents interviewed Omar al-Bayoumi Sunday night in the Red Sea port city of Jiddah, where he lives.
The FBI agents worked for the U.S. Embassy in Riyadh, said the official, who spoke on condition of anonymity. He gave no other details.
The White House has said it was eager to question al-Bayoumi, who a congressional report says befriended and helped al Qaeda members Khalid al-Mihdhar and Nawaf al-Hazmi, two of the hijackers on the jet that crashed into the Pentagon on Sept. 11, 2001.
Al-Bayoumi said Sunday in an interview with Dubai-based Al-Arabiya television that he was willing to talk with the FBI, but only in his homeland and in the presence of officials from his government. He told the station that he had done nothing wrong.
The Saudi government said last week it had authorized FBI and CIA agents in Saudi Arabia to question al-Bayoumi. The FBI sent a team to Saudi Arabia over the weekend as part of the investigation, a senior U.S. law enforcement official said.
It seems likely that al-Bayoumi will be interviewed again following Sunday night's questioning.
Al-Bayoumi studied in the United States on a Saudi government scholarship from 1994 to 2000. The congressional report said he and al-Mihdhar and al-Hazmi met in Los Angeles. When the two later moved into the same San Diego housing complex where al-Bayoumi lived, he threw them a welcoming party and put down money for their deposit and first month's rent, according to the report.
The FBI, according to the congressional report, found the connection "somewhat suspicious."
In earlier Saudi press reports, al-Bayoumi said the two men were mere acquaintances and briefly neighbors.
Al-Bayoumi also has several connections to the Saudi government, and some in Congress have alleged he could be a link between Saudi officials and the Sept. 11 suicide hijackings.
Al-Bayoumi left the United States two months before the attacks to study in Britain. British and U.S. officials investigated him immediately after the terrorist attacks and released him.
U.S. Attorney General John Ashcroft, asked about why the Americans might want to question al-Bayoumi again, said sometimes new information arises that makes it necessary to return to a person not originally considered important.
Osama bin Laden, the leader of the al Qaeda terrorist network, is accused of masterminding the Sept. 11 attacks. Bin Laden is Saudi by birth, but was excommunicated from his homeland in the mid-1990s for advocating violence against the United States and threatening to overthrow the Saudi royal family for allowing U.S. troops on Saudi soil during the 1991 Gulf War.
Secret parts of the congressional report into the Sept. 11 attacks examines interactions between Saudi businessmen and the royal family that may have intentionally or unwittingly aided al Qaeda or the suicide hijackers.
The Saudi government has urged Washington to publish the classified sections, saying they cannot otherwise respond to the allegations.