The FBI inadvertently revealed one of the U.S. government's most sensitive secrets about the Sept. 11 terror attacks: the identity of a mysterious Saudi Embassy official in Washington who agents suspected had directed crucial support to two of the al-Qaida hijackers. The disclosure came in a new declaration filed in federal court by a senior FBI official in response to a lawsuit brought by families of 9/11 victims that accuses the Saudi government of complicity in the terrorist attacks. The declaration ... represents a major breakthrough in the long-running case, providing for the first time an apparent confirmation that FBI agents investigating the attacks believed they had uncovered a link between the hijackers and the Saudi Embassy in Washington. The disclosure, which a senior U.S. government official confirmed was made in error ... shines a light on the extraordinary efforts by top Trump administration officials in recent months to prevent internal documents about the issue from ever becoming public. This shows there is a complete government cover-up of the Saudi involvement," said Brett Eagleson, a spokesman for the 9/11 families whose father was killed in the attacks. "It demonstrates there was a hierarchy of command that's coming from the Saudi Embassy to the Ministry of Islamic Affairs [in Los Angeles] to the hijackers." Ironically, the declaration identifying the Saudi official in question was intended to support recent filings ... barring the public release of the Saudi official's name and all related documents.