Field tests have indicated that the letters contained cornstarch (like the substance pictured right), but local hazardous-materials teams have been sent to handle and analyze the letters, which are being investigated by the FBI, U.S. postal inspectors and local cops.
"We are not commenting at this time on the content of the note," Special Agent Mark White said Tuesday in the FBI's Dallas office.
What's the big deal with cornstarch?
You'll recall after Sept. 11. 2001 when the threat of letter-borne anthrax made headlines. (This archive photo at left was taken in Washington D.C.)
-- Compiled by Bill Miller from the work of Domingo Ramirez Jr.