A letter addressed Wednesday to President Barack Obama was suspiciously similar to a letter that tested positive for the deadly poison ricin, NBC News said.
The letter was intercepted Tuesday at the U.S. Capitol's off-site mail facility in Washington. The test required to see if the letter contained ricin takes 24 to 48 hours to conduct, CNN said.
Ricin is a deadly and easily produced substance. An amount of 500 micrograms, as small as the head of a pin, can kill an adult.