CBS News reported last night that Department of Homeland Security officials uncovered a plot by al Qaeda in the Arabian Peninsula to poison food at hotels and restaurants in the U.S.

A key Intelligence source has confirmed the threat as "credible." Department of Homeland Security officials, along with members of the Department of Agriculture and the FDA, have briefed a small group of corporate security officers from the hotel and restaurant industries about it.

The plot uncovered earlier this year is said to involve the use of two poisons – ricin and cyanide – slipped into salad bars and buffets.

Manuals and videos on jihadist websites explain how to easy it is to make both poisons.

"Initially it would look very much like food poisoning," said St. John’s University professor of pharmaceutical sciences Dr. Susan Ford.

Former Homeland Security Secretary Michael Chertoff says it’s important to let public health officials know that what looks like food poisoning could be a terrorist attack.