Al Qaeda had planned to attack Los Angeles' tallest building in the months after Sept. 11 as part of a second wave of strikes that was never carried out, according to a statement by an alleged terrorist that was passed on to the Los Angeles Police Department.
"We were made aware of that information last spring," said John Miller, the LAPD's top anti-terrorism official. "From a public safety standpoint, we took a number of immediate steps to tighten our procedures on notifications of any hijackings in the area."
Miller said city agencies had also implemented evacuation drills at high-rise buildings in the downtown area after police learned of the alleged plot.
Two law enforcement sources said that Khalid Sheikh Mohammed, the former operations chief for Al Qaeda captured last March, reportedly told his interrogators that the Library Tower -- now known as the U.S. Bank Tower -- was targeted along with Chicago's Sears Tower.
Law enforcement officials, however, caution that Mohammed's statements since his capture have been viewed with a degree of skepticism by U.S. intelligence.
The Joint Terrorism Task Force, a government council made up of federal and local law enforcement officials, first learned about Al Qaeda's aborted plans for a second wave of attacks early last year, Miller said.
Federal officials declined to discuss any specifics. "We can't confirm any reports about Sheikh Mohammed's purported statements," said FBI spokesman Special Agent Matt McLaughlin. "But we've met with those who manage and own the Library Tower and other structures in the Los Angeles area in order to assess and improve security at those locations."
After the Sept. 11 attacks, security at the U.S. Bank Tower was tightened.
"Our team moved quickly to thoroughly review security and business practices, perimeter protection as well as security technology," said Ron Heckmann, a spokesman for Maguire Properties, the tower's owner.
"We budgeted $6.5 million for a variety of improvements as a result of that review," Heckmann said. "We also beefed up training for security and staff and redoubled response and readiness for tenant security, life safety and evacuations."
Heckmann said he could not comment on any specific threats.
According to law enforcement sources, Mohammed told interrogators that Al Qaeda initially planned to hit five targets on the East Coast and another five targets on the West Coast as part of a massive hijacked jet attack on Sept. 11, 2001.
But after it was decided that those attacks would be too difficult to synchronize, plans were hatched for two waves of attacks.
The second wave at a later date, law enforcement officials said, was to include the Library Tower, the tallest building in the West.