WASHINGTON, Aug. 21 — A report released Tuesday by the Central Intelligence Agency includes new details of the agency’s missteps before the Sept. 11 attacks, outlining what the report says were failures to grasp the role being played by the terror mastermind Khalid Sheikh Mohammed and to assess fully the threats streaming into the C.I.A. in the summer of 2001.

The 19-page report, prepared by the agency’s inspector general, also says 50 to 60 C.I.A. officers knew of intelligence reports in 2000 that two of the Sept. 11 hijackers, Nawaf al-Hazmi and Khalid al-Mihdhar, may have been in the United States. But none of those officers thought to notify the Federal Bureau of Investigation about the potential domestic threat, the report says, evidence of what it calls a systemic failure.

The inspector general recommended that several top agency officials, including former director George J. Tenet, be held accountable for their failure to put in place a strategy to dismantle Al Qaeda in the years before Sept. 11, 2001. Gen. Michael V. Hayden, the current C.I.A. director, and his predecessor, Porter J. Goss, have declined to seek disciplinary action against Mr. Tenet and others named in the report.

The outlines of the report have been known since shortly after it was completed in 2005, but it had never been made public, and its release reignited a debate about whether the C.I.A. should have done more before the attacks and whether Mr. Tenet and other officials should be held accountable.