Biden and Vice President-elect Kamala Harris have announced additional White House picks -- with many familiar faces from Biden's 2020 campaign staff.

While she was not expected to join the administration and instead return to her communication’s firm SKDKnickerbocker, Anita Dunn will be serving as a senior adviser to the president -- marking yet another longtime Biden adviser and a member of the highest echelons of his campaign joining the White House in a senior role.

TJ Ducklo, the national spokesperson for the campaign, will also join the White House as deputy press secretary alongside Karine Jean-Pierre. Deputy press secretary Matt Hill will join as a senior associate communications director.

Biden’s campaign photographer and videographer will also take on similar roles in the administration.

-ABC News' Molly Nagle

The House of Representatives' Committee on Oversight and Reform has sent letters to two dozen hotels and private travel companies seeking help in identifying rioters and preventing future attacks in Washington, D.C., ahead of Biden's inauguration.

"While the inciters and attackers bear direct responsibility for the siege on the Capitol and will be held fully accountable, they relied on a range of companies and services to get them there and house them once they arrived—companies that law-abiding Americans use every day, but whose services were hijacked to further the January 6 attacks," committee chairwoman Rep. Carolyn Maloney, D-N.Y., wrote in the letters. "Trump supporters chartered scores of buses and vans and drove in caravans to the nation’s capital. They stayed in D.C. hotels, with videos showing attackers relaxing in the lobby of one hotel after the insurrection."

The committee has asked the businesses -- ranging from major hotel chains to bus and car rental companies -- to retain records of January reservations for future congressional investigations, to put in place additional screening measures "to ensure that your services are not being used to facilitate violence or domestic terrorism," and to provide information to the committee by Jan. 29 on those measures.

-ABC News' Ben Siegel

The danger to the public and to law enforcement officers from explosive devices during expected upcoming protests "is substantial," the Federal Bureau of Investigation warned in a new awareness bulletin obtained by ABC News on Friday.

The document is full of photos of devices used in the last eight months against civilian and law enforcement targets during public demonstrations.

"Devices targeting infrastructure also increased following violent activity during this time period," the bulletin states.

The FBI now wants to make first responders aware of what has been deployed in the past and what they might encounter during protests linked to the presidential inauguration on Jan. 20.

"The danger posed to law enforcement officers and the general public from the all the tactics listed is substantial," the bulletin states. "If a suspicious item is reasonably believed to contain explosives, an IED, or other hazardous material, DO NOT touch, tamper with, or move the item. Only bomb disposal personal should handle any suspected devices that are located."

An internal FBI bulletin obtained by ABC News earlier this week stated that armed protests are being planned at all 50 state capitols as well as at the U.S. Capitol in Washington, least through Inauguration Day.

The warning comes after suspected pipe bombs were found last week outside both the Democratic National Committee and the Republican National Committee headquarters, just a few blocks from the Capitol where pro-Trump rioters stormed the building.

-ABC News' Aaron Katersky

Biden has chosen Dr. David Kessler, former commissioner of the Food and Drug Administration (FDA), to help lead the federal government's COVID-19 vaccine initiative.

Kessler, a pediatrician and lawyer who headed the FDA from 1999 to 1997 under the Bush and Clinton administrations, will replace Dr. Moncef Slaoui, who is the current chief science officer to Operation Warp Speed.

Biden also announced several other appointees who will join his incoming administration's COVID-19 response team.

"We are in a race against time, and we need a comprehensive strategy to quickly contain this virus," the president-elect said in a statement Thursday. "The individuals announced today will bolster the White House’s COVID-19 Response team and play important roles in carrying out our rescue plan and vaccination program. At a time when American families are facing numerous challenges I know these public servants will do all that is needed to build our nation back better."

Senate Majority Leader Mitch McConnell has indicated that the Senate impeachment trial should take place after Trump leaves office.

The Senate impeachment process will begin "at our first regular meeting following receipt of the article from the House," McConnell wrote in a new statement, saying he believes it would be best for the country to have an orderly transfer of power completed before a trial begins.

The Senate is currently scheduled to return to Washington on Tuesday, making that the earliest day for any Senate action related to the trial to occur -- but McConnell's message to House Speaker Nancy Pelosi and Democrats is for them not to send the articles until after Biden is sworn in.

McConnell has no control over when a trial begins -- that is determined by the articles sent to the Senate​​.

While House Speaker Nancy Pelosi has so far declined to say publicly when the House will send the article over to the Senate, a source involved in the Democratic leadership deliberations told ABC News earlier Wednesday Pelosi planned to send the article to the Senate next week.

"Even if the Senate process were to begin this week and move promptly, no final verdict would be reached until after President Trump had left office. This is not a decision I am making; it is a fact. The President-elect himself stated last week that his inauguration on January 20 is the ‘quickest’ path for any change in the occupant of the presidency," McConnell wrote.

"In light of this reality, I believe it will best serve our nation if Congress and the executive branch spend the next seven days completely focused on facilitating a safe inauguration and an orderly transfer of power to the incoming Biden Administration."

McConnell confirmed on the record earlier Wednesday that he is considering voting to convict Trump on inciting an insurrection.

-ABC News' Allison Pecorin