Suspicious substance in letter for Obama: Secret Service

Washington, April 17 (IANS) A US Secret Service spokesman Wednesday said a letter addressed to President Barack Obama contained "suspicious substance", reported Xinhua.

The spokesman said that the authorities intercepted the suspicious letter at the White House off-site mail facility.

The letter arrived Tuesday, the same day that another letter addressed to a senator was intercepted and initially tested positive for ricin, a highly toxic substance.

Lawmakers on the Capitol Hill confirmed that the Capitol Police intercepted a suspicious letter, which was addressed to Senator Roger Wicker, at an off-site postal screening centre Tuesday morning.

The incidents came one day after two explosions occurred near the finish line of the Boston Marathon, killing three people and wounding over 170 others. The authorities have called the Boston bombings an "act of terror," but the motives and perpetrators remain unknown.