Leahy anthrax letter to be opened Friday at military lab

The envelope addressed to Sen. Leahy has remained sealed since its discovery November 16.

By Susan Candiotti
CNN Washington

WASHINGTON (CNN) -- FBI scientists now expect Friday to be "opening day" for the anthrax-filled letter to Sen. Patrick Leahy, pushing back by a day when authorities thought they might be ready to slice open the envelope.

Sources told CNN the FBI has unanimous agreement on the precise method that will be followed, but no details were given.

The envelope addressed to the Vermont Democrat has remained sealed since it was discovered November 16 during a search of 280 barrels of sequestered mail. An FBI-lead team of investigators wearing hazardous material suits found the letter from among thousands set aside after a similar envelope to Senate Majority Leader Tom Daschle was discovered last month.

A group of scientists from the FBI, the U.S. military, and at least three outside scientists will examine, open and study the contents of the Leahy envelope.

The FBI has already described the anthrax that seeped through the envelope as matching the pure quality of the Daschle anthrax.

That Daschle anthrax is said to have been treated with silica, a common drying that would make it easier to lodge in the lungs of anyone close enough to breathe the anthrax spores.

The FBI expects this sample to be the most pristine of any anthrax recovered so far because fewer people have handled it.

Among the questions to be resolved:

Is the letter inside a perfect match of the one sent to Daschle? How much anthrax did the suspected killer intend to stuff inside the envelope? Does the anthrax mirror the Daschle anthrax in every respect?

This week, scientists have been practicing different ways to open the letter; for example, using a scalpel to slice it open.

Investigators want to preserve as much of the anthrax as possible to maximize their research.