02/23/2012 12:26 pm ET

Senate Offices Receive Threatening Letters With Suspicious Powder Found To Be Harmless

More U.S. Senate district offices have received letters containing a suspicious powder, though the powder has been found to be harmless, according to reports from CBS and National Journal Thursday. No details were available about which offices received letters.

The news comes after the Senate sergeant-at-arms, Terrance Gainer, announced Wednesday that three district offices received threatening letters with powder that was also deemed to be harmless. The district office of House Speaker John Boehner (R-Ohio) received one of the letters.

Jon Stewart and Stephen Colbert of Comedy Central also received letters.

The letters were postmarked from Portland, Oregon with phony addresses.