FBI investigation on poisonous ricin

The FBI ran an investigation, following a similar package to a US senator which contained ricin.

White House press secretary Jay Carney said at the press conference that there was no connection with the Boston bombings.

US President Barack Obama will travel to Boston tomorrow.

BBC reported that the envelope to the White House was received on Tuesday, referring to the information from US secret service. 

Ricin, from the castor oil plant Ricinus communis, is a highly toxic, naturally occurring protein. A dose as small as a few grains of table salt can kill an adult human, according wikipedia.