Remember the "ricin attack" on Congress last month? Remember what else was happening at that time?
There is a new theory emerging about the ricin scare two weeks ago.
NBC News has learned investigators are looking into the possibility that there never was any ricin attack in the first place.
A white powder, previously believed to be ricin, was discovered on a machine used to open envelopes in the Dirksen Senate office building. Dirksen and two other buildings were closed for several days.
There are several reasons for the new theory. Investigators haven't been able to determine an apparent source of the ricin, and the suspicous substances was found in very small amounts.
Since ricin comes from the castor bean, and some nontoxic parts of the plant are used to make paper, it might be possible that the tests found traces of the plant, but not ricin.
Investigators said there are no solid leads and this is just one of several theories.
NBC News: Ricin Tests May Have Been Wrong