FBI investigating a dozen envelopes with suspicious powders received by election workers in five states

Georgia, Nevada, Oregon, California and Washington are the five states where letters were received, some containing fentanyl.

The FBI and the Postal Inspection Service are analyzing a series of envelopes containing suspicious substances that where received by election workers and facilities in Georgia, Nevada, Oregon, California and Washington. In the latter, employees at four electoral offices had to be evacuated while they processed votes from last Tuesday's elections.

"Law enforcement agencies are working diligently to intercept any additional letters before they are delivered," read a statement issued Thursday by the FBI and the Postal Inspection Service and reported by NPR.

A senior official close to the investigation told CBS News that some of the twelve letters contained traces of fentanyl, and that the substances, taken as a whole, were not harmful to health. He also reported that investigators believe the letters were sent from the Pacific Northwest.

Local media outlet, Komo News, obtained images of the letter received at the Pierce County elections office, which forced workers to leave the building. Inside the envelope were slogans such as "end the elections now":