A Blackburn spokesman confirmed that the office had reopened Tuesday but had no details about the results of the investigation into the envelope received Monday.
The Leaf Chronicle reports that police evacuated part of the Federal Building after they were called to the congresswoman's offices there on Monday morning.
Clarksville police said they sent the suspicious envelope to the Tennessee Bureau of Investigation, but a TBI spokeswoman said the letter had been sent to the state Department of Health.
A spokesman at the Health Department had no immediate information about the envelope's contents.