The U.S. Secret Service says it has intercepted a letter addressed to President Barack Obama that contained a "suspicious substance."

Secret Service spokesman Ed Donovan says the letter was intercepted at a facility away from the White House. He says the letter was received Tuesday.

The letter comes a day after lawmakers said a letter was mailed to Sen. Roger Wicker that tested positive for poisonous ricin. Another senator said police have a suspect in mind.

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.