(CNN) - Capitol Police in Washington said they are investigating threatening statements made against Senate Majority Leader Harry Reid.
Police would not provide additional information other than to say it's an ongoing investigation.
A spokesman for the Nevada Democrat declined to comment.
Reid, who has a permanent security detail, is a sharp-elbowed politician who is outspoken on many topics and often clashes openly with conservatives on issues from Obamacare to budget matters.
But a congressional source said the threats started after Reid made sharply critical comments about supporters of controversial Nevada ranger Cliven Bundy, at one point calling them "domestic terrorists."
Bundy was locked in a high-profile and protracted land dispute with the federal government.
Last week, he drew widespread scorn for making racially insensitive comments.