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.
CBSNews.com Report: Terror in the U.S.
"We operate under the premise that individuals prepared to carry out terrorist acts are in this country," said Dec. of Homeland Security Janet Napolitano on Dec. 6, 2010.
The plot uncovered earlier this year is said to involve the use of two poisons - ricin and cyanide - slipped into salad bars and buffets.
Of particular concern: The plotters are believed to be tied to the same terror group that attempted to blow up cargo planes over the east coast in October, al Qaeda in the Arabian Peninsula.
In online propaganda al Qaeda in the Arabian Peninsula has praised the cargo attack, part of what it called "Operation Hemorrhage."
The propaganda says in part, "...attacking the enemy with smaller but more frequent operations" to "add a heavy economic burden to an already faltering economy."
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.
She showed how little of each poison could be fatal by putting a small amount of poison in cups.
Armen Keteyian: Are these dosages enough to really harm someone or kill someone?
Susan Ford: Yes, these are 250 milligrams and that is the fatal dose.
Keteyian: So just that much sodium cyanide is enough to kill me?
Ford: Yes, it is.
That leads to a difficult debate: The need to inform the public without alarming it.
Former Homeland Security Secretary Michael Chertoff said, "A threat you might feel is sufficiently specific and credible to tell the people who are professionally involved might not be specific or credible enough to tell the general public."
Chertoff says it's important to let public health officials know that what looks like food poisoning could be a terrorist attack.
On Monday Dept. of Homeland Security spokesman Sean Smith said, "We are not going to comment on reports of specific terrorist planning. However, the counterterrorism and homeland security communities have engaged in extensive efforts for many years to guard against all types of terrorist attacks, including unconventional attacks using chemical, biological, radiological, and nuclear materials. Indeed, Al-Qa'ida has publicly stated its intention to try to carry out unconventional attacks for well over a decade, and AQAP propaganda in the past year has made similar reference.
"Finally, we get reports about the different kinds of attacks terrorists would like to carry out that frequently are beyond their assessed capability."
The fact remains the government and hospitality industries are on alert.