Inside an opulent palace in Riyadh late one evening in February 2004, two American investigators interrogated a man they believed might hold answers to one of the lingering mysteries of the Sept. 11, 2001, attacks: What role, if any, did officials in Saudi Arabia’s government play in the plot?

The man under questioning, Fahad al-Thumairy, had been a Saudi consular official based in Los Angeles and the imam of a mosque visited by two of the hijackers. The investigators, staff members of the national 9/11 commission who had waited all day at the United States Embassy before being summoned to the late-night interview, believed that tying him to the plot could be a step toward proving Saudi government complicity in the attacks.

They were unsuccessful. In two interviews lasting four hours, Mr. Thumairy, a father of two then in his early 30s, denied any ties to the hijackers or their known associates. Presented with phone records that seemed to contradict his answers, he gave no ground, saying the records were wrong or people were trying to smear him. The investigators wrote a report to their bosses saying they believed Mr. Thumairy was probably lying, though no government investigation into the Sept. 11 attacks has ever found conclusive evidence that Mr. Thumairy — or any other Saudi official — assisted in the plot.

But nearly 15 years after the attacks on New York and Washington, the question of a Saudi connection has arisen again amid new calls for the release of a long-classified section of a 2002 congressional inquiry into the attacks that discusses a possible Saudi role in the terrorist plot — the so-called 28 pages, whose secrecy has made them almost mythical.

American officials who have read the 28 pages say that, of all the investigative leads in that section of the report, the unanswered questions about Mr. Thumairy and the two hijackers remain the most intriguing. If there was any Saudi government role whatsoever, some still believe, it most likely would have gone through Mr. Thumairy.

The fact that years of investigation found no hard proof of official Saudi involvement has led some, notably the Saudi government, to argue that it is now the stuff of wild conjecture and conspiracy theory. The material in the 28 pages has been thoroughly investigated, the Saudi foreign minister, Adel al-Jubeir, said during a news conference here on Friday, and “those investigations have revealed that these allegations are not correct.”

“There is no there there,” he said.

John O. Brennan, the director of the Central Intelligence Agency, said during a recent interview with the Saudi-owned Al Arabiya television network that while he supported the release of the 28 pages, “people shouldn’t take them as evidence of Saudi complicity in the attacks.” American investigations into 9/11, he said, concluded that the attacks were the work of “Al Qaeda, of Bin Laden” and “others of that ilk.”

But to some, all the circumstantial evidence provides a glimpse of a truth that has yet to be unearthed.

“It’s one of those cases where there are an awful lot of very troubling coincidences,” said Richard L. Lambert, who oversaw the investigation into the hijackers’ contacts as the assistant agent in charge of the F.B.I.’s San Diego office in the year after the attacks.

At the F.B.I., the Sept. 11 plot officially remains an open case. While there is broad agreement on how it unfolded, there are aspects of the investigation that remain unresolved. And the mystery begins with the arrival at Los Angeles International Airport on Jan. 15, 2000, of two Saudi men who more than year and a half later would be among the hijackers who crashed American Airlines Flight 77 into the Pentagon.

Apart from their proven devotion to the jihadist cause, the men, Nawaf al-Hazmi and Khalid al-Mihdhar, seemed unlikely choices for a pair of terrorists who would have to survive, and plot for months, in the United States. Neither spoke English or had experience navigating American life.

That circumstance would make it all the more critical for the F.B.I., after the attacks, to find out whether the two hijackers received help after reaching Los Angeles. But after an exhaustive canvass of hotels, investigators were unable to find any definitive evidence of where and how Mr. Hazmi and Mr. Mihdhar spent their first two weeks in the United States. By some accounts, however, they worshiped at the King Fahad Mosque in the Culver City area, where Mr. Thumairy was an imam, and they may have stayed in a nearby apartment rented by the mosque.

An F.B.I. document from 2012, cited last year by an independent review panel, concluded that Mr. Thumairy “immediately assigned an individual to take care of al-Hazmi and al-Mihdhar during their time in the Los Angeles area.” The review broadly upheld the conclusions of the 9/11 commission on Saudi involvement, and the F.B.I. has still not been able to fill other gaps in the timeline of those initial two weeks in January 2000.

When the two hijackers reappeared in early February, they were eating at a restaurant, Mediterranean Gourmet, near the mosque. There, they encountered Omar al-Bayoumi, a fellow Saudi who was on the Saudi government payroll through the country’s civil aviation authority, possibly with an assignment to keep an eye out for Saudi dissidents in California.

Mr. Bayoumi later told the F.B.I. that the meeting was happenstance — that he overheard Mr. Hazmi and Mr. Mihdhar, noticed their Gulf accents and struck up a conversation. But the bureau believed that Mr. Bayoumi had met with Mr. Thumairy at the mosque just before he met the hijackers in the restaurant, and investigators wondered whether Mr. Thumairy had arranged the meeting.

At the time, Mr. Thumairy was part of a network of representatives of the Saudi Ministry of Islamic Affairs, which finances mosque-building, trains clerics and proselytizes the conservative and intolerant strain of Islam known as Wahhabism. During his interview in Riyadh in 2004, Mr. Thumairy spoke fondly of his six years in Los Angeles, praising the warm weather and friendly people. His job at the consulate and the nearby mosque, he said, was to answer religious questions.

But investigators wrote that Mr. Thumairy appeared to be “deceptive” when questioned about his contacts, notably with Mr. Bayoumi. He denied knowing Mr. Bayoumi, despite telephone records that showed 21 calls between them over two years.

Whether out of charitable instincts or at someone’s direction, Mr. Bayoumi, then 42, helped the two future hijackers settle in San Diego, in the apartment building where he himself lived. He co-signed the lease and paid the security deposit and first month’s rent, though they reimbursed him.

Mr. Lambert, the former F.B.I. official in San Diego, said he was skeptical that the assistance was given by chance. With the 9/11 plot riding on the hijackers’ ability to manage daily life, he said, Qaeda leaders would most likely have made arrangements to get them help.

“I have to believe something was planned for the care and nurturing of these guys after they arrived,” he said. “They weren’t too sophisticated, and they didn’t speak English. They needed help getting settled and making preparations.”

There were other tantalizing suggestions of a possible network of supporters. Mr. Hazmi and Mr. Mihdhar began worshiping at a San Diego mosque where the imam was Anwar al-Awlaki, an American cleric who years later would became an infamous online recruiter for Al Qaeda. A Yemeni student named Mohdar Abdullah drove them around, helped them open bank accounts and connected them with flight schools. Two Saudi naval officers living in San Diego had telephone contact with Mr. Hazmi.

But it was the Thumairy-Bayoumi connection that some investigators found to be the most suspicious.

The first independent panel investigating the attacks, the Congressional Joint Inquiry, compiled a list of leads into the California part of the plot that it turned over to the F.B.I. and C.I.A. and eventually became part of the 28 pages withheld from the public version of the report. That section has remained classified even though the Saudi government has long called for its release. Mr. Jubeir, the Saudi minister, reiterated that call on Friday because, he said, his government could not “respond to blank pages.”

The questions about his government’s possible role are coming from several sources. The Senate unanimously passed a bill last month that would make it easier to sue the Saudi government for any role in the terrorist attacks, and the House might take up the bill next week. A lawsuit filed against Saudi Arabia on behalf of the families of those killed in the attacks continues its slow progress through the courts.

Eleanor J. Hill, the staff director for the congressional inquiry, cautioned that the 28 pages were not a Rosetta Stone that would decipher the enduring puzzles of 9/11.

“What the 28 pages are is a summary of the information given to the agencies for further investigation,” she said. “Nobody should be expecting that the 28 pages will give a final conclusion”

In a statement in April, Thomas H. Kean and Lee Hamilton, the 9/11 commission’s co-chairmen, insisted that they took all questions about a possible Saudi role in the plot seriously, following up on the leads in the 28 pages. They said that while the commission had “not found evidence” that Mr. Thumairy assisted the hijackers, he was “still a person of interest” in the case.

The commission’s final report said that “we have found no evidence that the Saudi government as an institution or senior Saudi officials individually funded” Al Qaeda. Today, some commission staff members point out that the wording did not rule out the possibility that lower-ranking Saudi officials had assisted the hijackers. They also said the commission operated under extreme time pressure and was not able to follow up fully on every lead.

Mr. Thumairy’s visa was quietly revoked in 2003 because American officials believed he was a “radical imam,” documents show. When he tried to return to Los Angeles from a trip home, he was detained for two days and sent back to Saudi Arabia. But he told his interrogators that night in 2004 that he would never have knowingly assisted terrorists.

“He said that he has always spread the message of peace, both in the U.S. and here in Saudi Arabia, and especially since 9/11,” the two commission investigators who questioned him, Dieter Snell and Rajesh De, wrote in their report on the interview.

“He said he wants to work with the U.S. and the Saudi government because terrorism hurts everyone.”

Authors: Scott Shane, Mark Mazzetti

Source: nytimes.com