Was positive reading in Senate office caused by paper byproducts?
NBC News and news services
Updated: 8:13 p.m. ET Feb. 18, 2004
WASHINGTON - Investigators seeking the source of the ricin detected two weeks ago in a Senate office building have raised the possibility that the positive test that forced the evacuation of lawmakers and staff members may have been caused by paper byproducts, not the deadly poison, NBC News has learned.
Sources familiar with the investigation, speaking on condition of anonymity, said that federal agents have found no source for the powder found in the mailroom of Senate Majority Leader Bill Frist?s office.
In addition to the apparent absence of a means of delivery, suspicions that the positive test might have been a false alarm have been heightened by the fact that the amount of the powder initially believed to be ricin was very small, precluding the performance of a potency test by the labs that received samples.
A possible explanation for the positive reading also has emerged. The sources said that investigators have determined that non-toxic byproducts of the castor bean plant ? the raw material for ricin ? are sometimes used in making paper. Because tests performed on congressional mail are highly sensitive, they could have picked up minute traces of products derived from the castor plant ? not actual ricin, according to this theory.