Sara Carter of the Washington Times offers this:

U.S. counterterrorism officials have authenticated a video by an al Qaeda recruiter threatening to smuggle a biological weapon into the United States via tunnels under the Mexico border, the latest sign of the terrorist group's determination to stage another mass-casualty attack on the U.S. homeland.

The video aired earlier this year as a recruitment tool makes clear that al Qaeda is looking to exploit weaknesses in U.S. border security and also is willing to ally itself with white militia groups or other anti-government entities interested in carrying out an attack inside the United States, according to counterterrorism officials interviewed by The Washington Times...

"The Americans are afraid that the [weapons of mass destruction] might fall into the hands of 'terrorist' organizations like al Qaeda and others," [al-Nafisi] told followers. "There is good reason for the Americans' fears. ... [Al Qaeda] had laboratories in north Afghanistan. They have scientists, chemists and nuclear physicists. They are nothing like they are portrayed by these mercenary journalists - backward Bedouins living in caves. No, no, by no means. This kind of talk can fool only naive people. People who follow such things know that al Qaeda has laboratories, just like Hezbollah."