United States (U.S.) capital Washington DC and many others states are under security lockdown ahead of Wednesday’s inauguration of President-elect Joe Biden.

The security beef-up came after Wednesday’s impeachment of President Donald Trump by the House of Representatives for “incitement of insurrection.”

It was the second time the House would impeach Trump, this time “for his role in the violent riot by a mob he inspired at the U.S. Capitol Building”.

The vote to impeach him passed the Democratic-controlled House by 232-197. Ten Republicans voted against Trump. It was the most bipartisan vote on a presidential impeachment in history.

It doubles the five Democrats who voted to impeach Bill Clinton in 1998.

The Senate is now required to begin the process of holding a trial to determine whether to convict Trump and potentially bar him from ever running for any office again.

Senate Majority Leader Mitch McConnell, R-Ky., said the trial would begin after the Senate reconvenes on Tuesday, the day before Biden is sworn into office.

Some airlines have put up new restrictions on passengers to the U.S. capital as Democrats warned of possible political violence even after Biden’s inauguration.

Delta will not allow travellers flying to Washington area airports to check firearms on its flights before the inauguration, its chief executive, Ed Bastian, said on Thursday.

The actions followed the storming of the U.S. Capitol last week by Trump’s supporters and disturbances on flights and at airports.

Officials have warned of plans by armed protesters in Washington and the 50 states.

The Capitol Building is now heavily guarded, swarming with thousands of National Guard members.

The Senate Historical Office said it was aware of only two other occasions during which troops stayed overnight in the Capitol: during World War II and during the riots in Washington in 1968.

Without consulting Republicans, Pelosi and the Democrats have installed metal detectors outside the House chamber doors. Even though everyone — Democrats included — must pass through the detectors, Republicans believe the security measure is aimed at humiliating them.

Hotels, airlines and other businesses ramped up security as authorities planned to deploy at least 20,000 National Guard troops in the city.

“We’re all on high alert based on the events over the last couple of weeks in Washington,” Bastian told CNBC. He told Reuters his airline had placed passengers on a no-fly list for their involvement in disruptive incidents that, for example, targetted Republican U.S. Senator Mitt Romney.

In Washington, the perimeter of a high fence surrounding the Capitol was pushed out to encompass the U.S. Supreme Court and the Library of Congress. Nearby roads were closed, and some businesses said they would shut down.

U.S. Representative Abigail Spanberger, a former CIA case officer with a background in terrorism, warned of possible political violence after the inauguration.

Also yesterday, Governor Mike DeWine announced the closure of the Ohio Statehouse and state office buildings in downtown Columbus for four days beginning from Sunday, January 17, to Wednesday, January 20, as part of safety measures for the Biden’s inauguration day.

“In the interest of public safety, the Ohio Statehouse will be closed this coming Sunday, Monday, Tuesday, and Wednesday. All state office buildings in downtown Columbus will be closed on these days as well,” said Governor Mike DeWine.

“Personnel will work from home or other alternate work locations.”

There are reports of demonstrations of supporters of Trump at the Ohio Statehouse in downtown Columbus planned for the weekend till on inauguration day.

Governor DeWine also signed a proclamation that “mobilises the Ohio National Guard to assist in ensuring that the laws of Ohio are faithfully executed and to assist state and local authorities with protecting the health, safety and welfare of the citizens of this state.”

He said 500 members of the National Guard have been activated to join the earlier 200 members in Washington DC for the January 20 inauguration event to assist federal authorities in the Washington D.C. area.

Columbus City Mayor Andrew Ginther, who was at the joint media briefing announced, “the stepped-up security regarding threats to our city and state leading up to the inauguration of President-Elect Joe Biden.”

“I encourage residents to avoid protests this weekend. Hate groups want confrontation to amplify their messages of divisiveness. Let’s not give it to them.”

“We are taking every measure — together — to assure the safety of our residents and institutions. That means activating the Ohio National Guard; that means collaboration between Columbus Police, Ohio Highway Patrol, Ohio Homeland Security and the FBI.”

At the joint briefing were Columbus Police Chief Thomas Quinlan, Ohio National Guard Maj. Gen. John Harris, Jr., and Ohio State Highway Patrol Superintendent Col. Richard Fambro.

The storming of the Capitol is being investigated by federal authorities, who have arrested dozens of people so far.

More than 30 House Democrats, including Spanberger and U.S. Representative Mikie Sherrill, have asked the acting House and Senate sergeants-at-arms and the acting head of the Capitol Police for visitor logs, videos and other information about who was in the building that day.

Sherrill, who has accused Republicans of inciting the Trump mob, said she saw colleagues leading groups on “reconnaissance” tours of the Capitol the day before the January 6 attack.