Via CNN and television reports:

An envelope that tested positive for the deadly poison ricin was intercepted Tuesday afternoon at the U.S. Capitol’s off-site mail facility in Washington, congressional and law enforcement sources tell CNN.

After the envelope tested positive in a first routine test, it was retested two more times, each time coming up positive, the law enforcement source said. The package was then sent to a Maryland lab for further testing.

The envelope was addressed to a U.S. senator, though the sources would not say which one.

Ricin is a highly toxic substance derived from castor beans. As little as 500 micrograms — an amount the size of the head of a pin — can kill an adult. There is no specific test for exposure and no antidote once exposed.

The Senator has since been identified as Wicker.

Although he was one of 16 Republicans to vote to start debate on the gun control bill, he announced yesterday he would vote against it.

Just yesterday Wicker sent out this tweet: