The FBI has released the first document related to its investigation into Saudi Arabia’s involvement in the 9/11 attacks, following an executive order issued by US President Joe Biden.

The recently declassified document, dating from 2016, provides details of the FBI's work to investigate alleged logistical support that a Saudi consular official and a suspected Saudi intelligence agent in Los Angeles provided to at least two of the men who hijacked the planes which hit the Twin Towers on 9/11, according to CNN.

The document, released on the 20th anniversary of the attacks, details multiple communications and witness testimony that prompted the FBI to suspect "Omar al-Bayoumi", allegedly a Saudi student in Los Angeles but whom the FBI suspects of being a Saudi intelligence agent. 

The FBI document describes him as "as deeply involved in providing travel assistance, lodging, and financing to help the two hijackers."

Earlier, the Saudi embassy in the US welcomed the release of the FBI documents, announcing that "any allegations that Saudi Arabia was complicit in the 9/11 attacks are categorically false."

The embassy indicated at the time that previous investigations, including the September 11 commission and the release of the so-called "28 pages", revealed that "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 in its planning or execution.”

Last week, US President Joe Biden signed a decree declassifying some materials related to the 9/11 attacks in 2001.

He said, "When I ran for president, I made a commitment to ensuring transparency regarding the declassification of documents on the September 11, 2001 terrorist attacks on America [...] As we approach the 20th anniversary of that tragic day, I am honoring that commitment."."

The September 11, 2001 attacks targeted the two main trade towers in the World Trade Center and the US Department of Defense, killing about 3,000 people.