The FBI has released the first document related to its investigation of the 11 September 2001 attacks on the United States and allegations of Saudi government support for the hijackers, following an executive order by President Joe Biden.
Relatives of the victims had called on Mr Biden to skip memorial events to mark yesterday's 20th anniversary if he did not declassify documents that they have contended will show Saudi Arabian authorities supported the plot.
The partially redacted 16-page document released by the FBI outlined contacts between the hijackers and Saudi associates, but no evidence the government in Riyadh was complicit in the attacks, which killed nearly 3,000 people.
Saudi Arabia has long said it had no role in the attacks. The Saudi embassy in Washington did not immediately respond to a request for comment sent out of hours late yesterday.
In a statement issued on 8 September, the embassy said Saudi Arabia has always advocated for transparency around the events of 9/11, and welcomes the release by the United States of classified documents relating to the attacks.
"As past investigations have revealed, including the 9/11 Commission and the release of the so-called '28 Pages,' no evidence has ever emerged to indicate that the Saudi government or its officials had previous knowledge of the terrorist attack or were in any way involved," the embassy's statement said.
Fifteen of the 19 hijackers were from Saudi Arabia.
A US government commission found no evidence that Saudi Arabia directly funded Al-Qaeda, the group given safe haven by the Taliban in Afghanistan at the time. It left open whether individual Saudi officials might have.
The families of roughly 2,500 of those killed, and more than 20,000 people who suffered injuries, businesses and various insurers, have sued Saudi Arabia seeking billions of dollars.
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In a statement on behalf of the organisation 9/11 Families United, Terry Strada, whose husband Tom was killed on 11 September, said the document released by the FBI on Saturday put to bed any doubts about Saudi complicity in the attacks.
"Now the Saudis' secrets are exposed and it is well past time for the Kingdom to own up to its officials' roles in murdering thousands on American soil," the statement said.
The document from 4 April 2016 showed links between Omar Bayoumi, at the time a student but suspected to have been a Saudi intelligence operative, and two of the Al-Qaeda operatives who took part in the plot to hijack and crash four airliners into targets in New York and Washington.
Based on 2009 and 2015 interviews with a source whose identity is classified, the document details contacts and meetings between Bayoumi and the two hijackers, Nawaf al Hazmi and Khalid al Midhar, after the two arrived in Southern California in 2000 ahead of the attacks.
It also strengthens already-reported links between the two and Fahad al Thumairy, a conservative imam at the King Faad mosque in Los Angeles and an official at the Saudi consulate there.
The document says that telephone numbers associated with the source indicated contact with a number of people who assisted Hamzi and Midhar while they were in California, including Bayoumi and Thumairy, as well as the source himself.
It says the source told the FBI that Bayoumi, beyond his official identity as a student, had "very high status" in the Saudi consulate.
"Bayoumi's assistance to Hamzi and Midha included translation, travel, lodging and financing," the memo said.
It also said that the FBI source's wife told them Bayoumi often talked about "jihad."
And it further connects by meetings, phone calls and other communications, Bayoumi and Thumairy with Anwar al Alaki, the US-born cleric who became an important Al-Qaeda figure before he was killed in a drone strike in Yemen in 2011.
The document released was still significantly redacted and did not offer a clear direct link between the Saudi government and the hijackers.
Three successive US administrations have refused to declassify and release documents related to the case, apparently because they do not want to damage the US-Saudi relationship.
Jim Kreindler, one of the leaders of the lawsuit, said the document validates the lawsuit's key contention that the Saudi government helped the hijackers.
"With this first release of documents, 20 years of Saudi Arabia counting on the US government to cover up its role in 9/11 comes to an end," Mr Kreindler said in a statement.
The families are still hoping for stronger evidence when more classified material is released inside the next six months, based on a Biden order.