The Senate went into lockdown Wednesday afternoon as US Capitol Police investigated reports of an active shooter in the Russell office building, putting Capitol Hill on edge more than two years after the January 6, 2021, attack.

But after some staff fled from the building following a concerning phone call and police instructed others on the Senate side of the Capitol to shelter in their offices with their doors locked, law enforcement authorities found no evidence of an active shooter, according to multiple sources.

US Capitol Police Chief Tom Manger told reporters it "may have been a bogus call," and that there was no confirmation of an active shooter after more than 200 police officers went door-to-door to make sure everything was fine.

"So far, nothing. ... Nobody has heard shots" and "no victims," he added. All three Senate office buildings have been cleared of any threats.

A spokesperson for the Metropolitan Police Department says there is "no evidence of anyone injured" and at the moment, they are "unable to substantiate" the call.

The tense afternoon comes as security in Washington begins to ramp up ahead of former President Donald Trump's expected appearance on Thursday in a federal courthouse situated several blocks from the US Capitol. Trump was indicted Tuesday on criminal charges by a federal grand jury in special counsel Jack Smith's investigation into efforts to overturn the 2020 election leading up to the January 6 attack on the US Capitol.

On Wednesday, Senate staff received an alert from USCP came just before 3 p.m. EST.

"Due to a security threat inside the building, immediately: move inside your office or the nearest office; take emergency equipment and visitors; close, lock and stay away from external doors and windows," and "If you are in a public space, find a place to hide or seek cover," among other directions.

A social media post kicking off the scramble from USCP at 2:45 p.m. EST said, "Our officers are searching in and around the Senate Office Buildings in response to a concerning 911 call."

"If you are inside the Senate Buildings, everyone inside should be sheltering in place as the report was for a possible active shooter. It should be noted that we do not have any confirmed reports of gunshots," the post continued.

Lawmakers are out of Washington on their August recess.