The F.B.I and Capitol Police are investigating a suspicious package containing white powder that was sent to Republican Sen. Rand Paul's home in Bowling Green, Kentucky, Politico first reported Monday.

Details: It's not yet known who sent the package, but Paul tweeted that he takes "these threats immensely seriously."

What he's saying: "As a repeated target of violence, it is reprehensible that Twitter allows C-list celebrities to encourage violence against me and my family," Paul said in the Twitter post.

• He added in another tweet that he has been "targeted multiple times now."

Editor's note: This a breaking news story. Please check back for updates.