Final labs results are expected to be ready Tuesday on the powdery substance discovered Feb. 18 in a letter delivered to the Sevier County Courthouse, according to the FBI.
Also, federal authorities are looking at whether someone from outside the East Tennessee area sent the letter containing the unknown powder, according to Supervisory Special Agent Marshall Stone of the FBI's Knoxville office.
The powder was being tested at a Knoxville lab of the Tennessee Department of Health, Stone said Monday.
Preliminary testing last week indicated it was not harmful. Final results Tuesday should resolve what it is, he said.
Stone said the FBI is working with area local agencies on the case.
An employee of the 4th Judicial District Attorney General's Office opened the letter at the courthouse. As a precaution that employee and five others were taken to an area hospital to be checked. No one was harmed.
The Sevier County Sheriff's Department, Sevier County Emergency Management Agency, Sevierville Fire Department, FBI, TBI and Tennessee Emergency Management Agency responded to the call.
One person had direct contact with the substance, the TBI said last week.