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 was filed last month but unsealed late last week. According to a spokesman for the 9/11 victims’ families, it 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.