Capitol Police investigating threat against Rubio

The U.S. Capitol Police force is investigating a reported threat against U.S. Sen. Marco Rubio of Florida, who is often mentioned as a possible vice presidential pick for likely GOP presidential nominee Mitt Romney.

Capitol Police Lt. Kimberly Schneider said Wednesday she could not provide details of the investigation. Rubio's office and the FBI declined to comment.

U.S. Capitol Police confirmed to Fox News that there is an open and joint investigation with local police over a reported threat against Rubio. No further details were provided.

Rubio is scheduled to give a foreign policy speech in Washington, D.C., on Wednesday afternoon.

He recently stirred national debate with a new proposal to grant certain illegal immigrants the right to work in the U.S.

The Associated Press contributed to this report.