Deb Feyerick is on that breaking story. She joins us now.

--So, what do investigators know about the letters?

--Well, Anderson, right now, what they know is that they believe both of the letters were sent by the same person. The postmark was the same, they contained the same kind of substances, and they also both threatened Mayor Michael Bloomberg for his positions on guns, specifically those illegal guns. The Mayor reacted just a short time ago.

--Let me tell you, we're confident at the NYPD and the FBI, and their procedures. We take a lot of security massures, as you know. The men and the women that opened the mail, for example, even they're well trained. We have procedures for something like this. This is not the first letter that was ever sent to anybody.

In terms of why they've done this, I don't know. The letter was obviously referred to our anti-gun efforts. But there are 12,000 people are gonna get killed this year with guns, and 19,000 are gonna committ suicide with guns. We are not gonna walk away from those efforts.

--And Anderson, the police spokesman tells us that in fact the two letters contain sort of the pink orange oily substance. And in initial tests on the substance, initially were negative; then the second test found, was found to be positive. So now, that substances have been analyzed by the National Biofriends Analyst Center in Maryland, and the results of those tests should be definitive in the next day or tow, Anderson.

--Was anyone actually exposed we know about?

--There are a couple of people that were exposed. The mayor was not one of them, one of them in New York went to a mail facility, the one in Washington went to its organization, Mayors Against Illegal Guns. New York Emergency Services Unit, the police who responded to that they did initially tests develops some symptomes, some intestinal symptomes. But after a day or so, those went away and clearly, they've been monitered just protectively. Anderson.

--And obviously they're gonna be looking the letter's for DNA evidence or trace evidence that maybe there.

--Yeah, absolutely. Right now, investigators from both the FBI JTTF, the Joint Terrorism Task Force, as well as the NYPD. They're looking at the very specific location. The postmark that was on those letters clearly giving them some indications is to where the person who sent them might live. Anderson.

--All right. Joins us now is national security analyst in former Gerge W. Bush, homeland security advisor, Fran Townsend. She currently assists on the CIA and the DHS external advisor panels. Also on the phone, chief medical correspondent Dr. Sanjay Gupta.

So Fran, we have a report of the letters mentioned the gun control debate over Joint Terrorism Task Force investigating. It could be more of a political threat than a terror threat, really?

--That's right, Anderson. But as you've mentioned, that's not really at the moment the most relevent piece to the investigators, they don't much care about motive at the moment, they wanna know who. And so to determine the who, they'll look for the forensics, they'll look for the things like slight of hair, finger prints on the letter or on the envelop. They'll analyse automatically the handwriting. But all these things take time which is why the first thing they're gonna focus on is one the lab analysis, you heard Deb Feyerick, the first field test was negative, the second was positive. Oftentimes, these field tests are wrong which is why they're getting a real thorough lab result. That don't take a little bit of time. But that will tell them something, they'll understand the strength in the component, how competently it was mixed. They'll analyse whether the two letters, whether were from the same batch of mixure of the component of ricine. All those things will help investigators lead down the path to who. Once you determine the who, you will be able to understand the why.