A letter addressed to President Barack Obama is being checked for a "suspicious substance," a day after a letter addressed to a U.S. senator tested positive for poisonous ricin, the U.S. Secret Service says.
The letter to Obama arrived Tuesday and was intercepted at a facility away from the White House, said Secret Service spokesman Ed Donovan.
Word of the letter comes a day after lawmakers disclosed that a letter mailed to Sen. Roger Wicker tested positive for poisonous ricin. That letter to Wicker, a Republican, was intercepted at a Senate mail facility just outside Washington
Tensions have been high in Washington and across the country since the deadly bombings on Monday at the Boston Marathon that killed three people and injured more than 170.
Sen. Claire McCaskill has said authorities have a suspect in mind in Wicker case, though no one has been charged.
"The person that is a suspect writes a lot of letters to members," she said Tuesday as she emerged from a classified briefing.
Authorities declined to comment on a suspect or any other aspect of the investigation being led by Capitol Police and the FBI.