A U.S. report has criticized the Federal Bureau of Investigation for missing key information about terrorists planning the September 11, 2001 attacks, more than a year before the strike.

The Justice Department issued the report Thursday, saying FBI officials had at least five chances to discover two of the airline hijackers as they prepared for the attacks, but failed to do so.

In one case, it says an agent working for the Central Intelligence Agency (CIA) was blocked by a supervisor from sending information on the hijackers to FBI officials.

Attorney General Alberto Gonzales told NBC's Today show that reforms have been made to increase intelligence sharing among U.S. authorities, following the attacks.

Publication of the report had been stalled for a year, due in part to legal challenges by Zacarias Moussaoui, who pleaded guilty this year to a role in the attacks.

Some information for this report provided by AP.