The U.S. Capitol Police Department says it is taking seriously intelligence about a possible plot by a militia group to breach the Capitol on Thursday.
"We have already made significant security upgrades to include establishing a physical structure and increasing manpower to ensure the protection of Congress, the public and our police officers," the Capitol Police said in a statement. "Our department is working with our local, state, and federal partners to stop any threats to the Capitol."
The building where Congress meets has been protected with the help of National Guard troops and surrounded by an extended security perimeter with tall fencing since a Jan. 6 attack on the Capitol by supporters of then-President Donald Trump.
That mob breached the Capitol as members of Congress met to certify President Joe Biden's election victory over Trump.
Thursday's date is connected to a far-right conspiracy theory that Trump, who has repeatedly falsely claimed mass voter fraud cost him the election, would return to power on March 4. That date was inauguration day for U.S. presidents until 1933, when it was moved to Jan. 20.
Earlier this week, the FBI and Department of Homeland Security warned local law enforcement officials in a joint intelligence bulletin that a group of militia extremists had discussed encouraging people to travel to Washington and try to take control of the Capitol.
The threats prompted the House of Representatives to cancel its Thursday session. The Senate is scheduled to meet.
Lawmakers have held several hearings about what was known before the Jan. 6 attack and how local and federal agencies responded.
The Justice Department has charged more than 300 people with taking part in the siege that left five people, including a Capitol Police officer, dead.