WASHINGTON  Three weeks before a Jordanian double agent set off a bomb at a remote Central Intelligence Agency base in eastern Afghanistan last December, a C.I.A. officer in Jordan received warnings that the man might be working for Al Qaeda, according to an investigation into the deadly attack.

But the C.I.A. officer did not tell his bosses of suspicions  brought to the Americans by a Jordanian intelligence officer  that the man might be planning to lure Americans into a trap, according to the recently completed investigation by the agency. Later that month the Qaeda operative, a Jordanian doctor, detonated a suicide vest as he stood among a group of C.I.A. officers at the base.

The internal investigation documents a litany of breakdowns leading to the Dec. 30 attack at the Khost base that killed seven C.I.A. employees, the deadliest day for the spy agency since the 1983 bombing of the American Embassy in Beirut. Besides the failure to pass on warnings about the bomber, Humam Khalil Abu-Mulal al-Balawi, the C.I.A. investigation chronicled major security lapses at the base in Afghanistan, a lack of war zone experience among the agency’s personnel at the base, insufficient vetting of the alleged defector and a murky chain of command with different branches of the intelligence agency competing for control over the operation.

Some of these failures mirror other lapses that have bedeviled the sprawling intelligence and antiterrorism community in the past several years, despite numerous efforts at reform.