Earlier Thursday, Homeland Security Secretary Janet Napolitano told reporters that intelligence officials had picked up "lots of chatter" on jihadi websites and elsewhere about the impending 10th anniversary of the September 11 terrorist attacks "and we're taking it all seriously," but nothing yet that warranted issuing a threat advisory.

Nonetheless, the department will be at a heightened level of readiness as the nation commemorates the anniversary, "staffing up" the Federal Air Marshals Service and other agencies, she said.

"We don't have something that would reach that standard (of a credible threat), but we still have lots of chatter out there. And we take every bit of that seriously and are tracking it down," Napolitano said. "In the intel world, there's lots of chatter, and we're taking it all seriously. And should there be something that rises to the level where I have to issue a threat advisory, we will issue a threat advisory."

A federal official told CNN's Mike Ahlers that Napolitano was aware of the threat when she made those remarks.

Napolitano said it is not uncommon to see increased chatter before major events. "We know it's an iconic day to al Qaeda, in part because of what was found at the (Osama bin Laden) compound. So we are preparing accordingly," she said.

"I don't want to give those (details) out because I don't want to tell the bad guys exactly what we're doing," Napolitano said. "But I think it's fair to say that in addition to asking citizens to be vigilant and so forth, that we have ourselves leaned forward and have made sure that we are doing all that we can from the DHS perspective."

In other words, I don't think all those on the "list" are given precise instructions on how to disseminate the intel.