Senator Carl Levin's office is back open as usual this morning after a suspicious letter forced evacuations at the Saginaw building.
The letter tested negative for poison and suspicious materials, Levin said in a release this morning.
"I have been advised by the FBI that preliminary testing by the Michigan Department of Community Health, Micro-Biology Laboratory in Lansing showed negative results in the suspicious letter received by my Saginaw office," Levin said.
The office was evacuated yesterday afternoon after a staffer found a "suspicious" piece of mail.
The letter was not opened, and was handed over to the authorities for an investigation.
The staffer who found the letter was kept overnight at a local hospital for precautionary reasons, but was not displaying symptoms.
The suspicious letter came after letters that tested positive for ricin, a poison, was sent to President Obama and Mississippi Senator Roger Wicker.
The FBI said those letters were related and were both postmarked out of Memphis.
Paul Kevin Curtis, of Mississippi, was arrested Wednesday in connection with the letters. He reportedly believed he had uncovered a conspiracy to sell human body parts on the black market and claimed "various parties within the government" were trying to ruin his reputation.