The Republican National Committee headquarters in Washington, D.C., was under lockdown Wednesday morning after someone sent vials of blood to the building, three sources familiar with the situation told NBC News.

A hazardous materials team from the U.S. Capitol Police is on site.

The suspicious package was cleared, the Capitol Police told NBC News. But one of the sources familiar with the situation said the building was still on lockdown and the blood was being tested.

It is unclear if a suspect is in custody.

This is a breaking news story. Please check back for updates.