Officials believe a prison inmate may be behind a white powder scare earlier in the week.
Police responded to a call around 2 p.m. Monday after a receptionist at the Federal Court Building in Des Moines opened a letter that had a white powdery substance in it. There was a note in the envelope that contained a threat and identified the substance as toxic.
Officials with the U.S. Attorney General’s Office say the return address on the letter is from an out of state prison.
The powdery substance in Monday’s incident was acetaminophen, similar to what’s found in Tylenol.
Authorities believe the inmate may have sent a similar threatening letter with powder once before.