The U.S. House of Representatives cancelled its planned Thursday's session after the Capitol Police warned on Wednesday of a "possible plot" by a militia group to breach the building, a threat that echoed the deadly riots on January 6.

The House had been scheduled to debate and vote on a police reform bill, but a Democratic aide said plans changed partially due to the police warning, based on intelligence that "an identified militia group" could present a security threat.

The Senate will convene as planned to begin debating U.S President Joe Biden's COVID-19 relief bill worth $1.9 trillion on Thursday.

Some QAnon conspiracy theorists have said that Trump will be sworn in for a second term on Thursday (March 4) because that was the original Inauguration Day for presidents until 1933, when it was moved to January 20.

The Capitol Police said in a statement that it has obtained intelligence about the plot planned by an "identified militia group" and already made "significant security upgrades" to the Capitol starting earlier this week.

"The United States Capitol Police Department is aware of and prepared for any potential threats towards members of Congress or towards the Capitol complex," it said in its statement.

The security upgrades include "establishing a physical structure and increasing manpower to ensure the protection of Congress, the public and our police officers," said the statement, adding that the force is "working with our local, state, and federal partners to stop any threats to the Capitol."

The Justice Department has charged more than 300 people with taking part in the January Capitol siege, in which five people, including a police officer were killed. Among those arrested were members of the right-wing groups called the Oath Keepers, Three Percenters and Proud Boys. The Oath Keepers and Three Percenters are armed militia groups.

On Tuesday, Acting House Sergeant at Arms Timothy Blodgett notified Congress members of a possible security threat spanning Thursday through Saturday. It referred to "potential protests and demonstration activity surrounding what some have described as the 'true Inauguration Day.'"

Acting Capitol Police Chief Yogananda Pittman testified to Congress on February 25 that Trump supporters who launched the January attack have indicated they want to "blow up" the building and kill lawmakers.

Security has been tight around the Capitol since the January 6 riot which interrupted Congress' electoral vote count of U.S. President Joe Biden's victory. Five people died in the attack, including a Capitol police officer.

Christopher Wray, director of the FBI, said on Tuesday that the law enforcement agency classifies the January 6 Capitol riot by Trump's supporters as domestic terrorism.

The House impeached Trump on January 13 on a charge of inciting an insurrection, focusing on an incendiary speech he made to supporters shortly before his supporters converged on the Capitol. The Senate acquitted him on February 13.

(With inputs from Reuters, Xinhua)