Rep. Mikie Sherrill and 33 other House members want an investigation into access given by fellow House lawmakers to visitors to the Capitol on Jan. 5 before the violent attacks on Congress the next day.

The New Jersey Democrat alleged Tuesday night that members of Congress led guests on what she described as “reconnaissance” ahead of the insurrection on Jan. 6.

A letter issued Wednesday asks the acting House sergeant-at-arms, acting Senate sergeant-at-arms, and United States Capitol Police to investigate “suspicious behavior” on Jan. 5 and changes to visitor access.

“The visitors encountered by some of the Members of Congress on this letter appeared to be associated with the rally at the White House the following day,” Sherrill wrote.

The New Jersey Democrat and former Navy pilot first made public her concerns about House members preparing rioters for their siege of the Capitol in a video on Facebook on Tuesday night.

The letter notes that she and other signatories, including former CIA officer Abigail Spanberger, have served in military and intelligence roles and are trained to recognize suspicious activity.

“Members of the group that attacked the Capitol seemed to have an unusually detailed knowledge of the layout of the Capitol Complex. The presence of these groups within the Capitol Complex was indeed suspicious. Given the events of January 6, the ties between these groups inside the Capitol Complex and the attacks on the Capitol need to be investigated,” wrote the lawmakers.

Visitors, official tour groups and almost anyone without a congressional ID have been barred from the Capitol since mid-March, when the threat of the COVID-19 pandemic led congressional leaders to partially close the usually public building.

But members of Congress have been disregarding those strictures to bring in families and friends for small private tours for months, and Capitol Police stationed at entrances typically don’t challenge lawmakers to enforce rules.

The letter asks if there is a database of guests to the Capitol and if SAA staff and Capitol Police require lawmakers to sign in guests upon entry. They also want to know if facial recognition software is in use for visitors entering the Capitol complex.

“The tours being conducted on Tuesday, January 5, were a noticeable and concerning departure from the procedures in place as of March 2020 that limited the number of visitors to the Capitol. These tours were so concerning that they were reported to the Sergeant at Arms on January 5,” Sherrill and others wrote.

Majority Whip James E. Clyburn is not a signatory on the letter, but he has raised questions about how rioters knew some of the most hidden, obscure destinations in the Capitol to target and loot.

Clyburn’s second-floor office, with his name above the door, remained untouched during the destruction and violence last week. But a more private office, which is unmarked on the third floor, was targeted.

“There are many members of the United States Congress right now who could not tell you where that office is and could not find that office if they needed to,” the South Carolina Democrat told MSNBC.

“Yeah, but they found it. Nobody touched the door where my name is,” he said.

He said a thorough investigation is needed, and he questioned how the insurrectionists knew how to find an unmarked office of one of the top members of the House.

The Capitol Police Inspector General has already opened an investigation into the Jan. 6 attack, including officer conduct and potential failures of planning and leadership.

Many questions have been raised about how rioters got so deep into the Capitol without being stopped or apprehended, including looting the Senate chamber and breaking into and posing for pictures in Speaker Nancy Pelosi’s office.

There is also a sprawling federal investigation into the mob that stormed the Capitol. Michael Sherwin, the acting U.S. attorney for the District of Columbia, stressed Tuesday that the scope and scale of the probe means it would take months to uncover what happened when thousands of supporters of President Donald Trump surrounded the building and flooded the halls of Congress.

Chris Marquette and Todd Ruger contributed to this report.