SPOKANE - The downtown post office was evacuated Thursday morning after a report of a threatening letter.

KREM 2

Spokane hazardous material crews responded to a report of a foreign substance in a letter sent to the downtown post office.

A foreign substance was found in the package prompting the evacuation.

The letter tested negative and employees returned to work just before noon. The substance turned out to be an antacid.

Authorities say the letter was sent from Florida by a federal inmate who has a previous history of such behavior.