Omar al-Bayoumi was interviewed Sunday night by FBI agents in the Red Sea port city of Jiddah, where he lives, said the official, who spoke on condition of anonymity.
He said the FBI agents were connected to the U.S. Embassy in Riyadh but gave no details.
The White House said Monday it was eager to question al-Bayoumi. A congressional report says he befriended and helped al-Qaida members Khalid al-Midhar and Nawaf Alhazmi, 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 of that 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 this weekend, this time by the FBI team sent by Washington.
Al-Bayoumi studied in the United States on a Saudi government scholarship from 1994 to 2000. The congressional report said he and al-Midhar and Alhazmi met in Los Angeles. When the two moved into the 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 report, found the connection "somewhat suspicious."
In earlier Saudi press reports, al-Bayoumi said the two men were mere acquaintances and briefly neighbors.
He 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.
Also yesterday, the Ministry of the Interior said one of the militants killed in a shootout with Saudi police last week was part of a cell of 19 suspected terrorists linked to al-Qaida and thought to be behind bombings carried out May 12 by nine suicide attackers in Riyadh.
The statement carried by the official Saudi Press Agency named him as Ahmed bin Nasser al-Dekhiel.
The bombings, which killed 26 people, including nine Americans, sparked an anti-terror crackdown in the kingdom, with more than 200 suspects arrested and more than a dozen people killed.
Secretary of State Colin L. Powell said Saudi Arabia has been "especially aggressive" in responding to U.S. terrorism requests, although "we still have issues with respect to financing."