WASHINGTON — Twelve National Guard members have been removed from duties related to the inauguration of President-elect Joseph R. Biden Jr., two of them for expressing anti-government sentiments, Defense Department officials said on Tuesday.
Two of the members were removed over texts and social media posts that made threatening comments toward political officials, Pentagon officials said. They declined to specify the exact nature of the threats.
“I will share that they were inappropriate,” Gen. Daniel R. Hokanson, the chief of the National Guard Bureau, told reporters during a telephone briefing.
Two officials described the texts as broad in nature — not directed specifically at Mr. Biden or Vice President-elect Kamala Harris, but rather at lawmakers as a whole. One of the service members removed, the officials said, made a point of expressing support for President Trump in addition to making menacing comments.
General Hokanson said that one case was reported by the service member’s chain of command and that the other was flagged through a tip to a hotline.
The other 10 National Guard members were removed for a wide variety of issues — criminal investigations, domestic abuse or outstanding complaints. All 12 members have been sent home, Pentagon officials said.
The announcement of the removals came as the Pentagon was intensifying efforts to identify and combat white supremacy and other far-right extremism in its ranks, and as federal investigators sought to determine how many military personnel and veterans joined the violent assault on the Capitol on Jan. 6. The effort seems intended to remove any members whose social media posts or past actions raise suspicion.
General Hokanson noted that the authorities were not taking any chances one day before the inauguration and as investigators have expressed concerns that some extremists may try to impersonate National Guard members by wearing military uniforms.
“At this point we don’t have the time to run down every single piece of information,” he said. “But there’s enough information for us to determine to remove them from the Capitol.”
General Hokanson and other Pentagon officials took pains to say that most National Guard members — volunteer citizen-soldiers — put their lives on the line at home and abroad to protect the United States and the Constitution.
Senator Jack Reed, Democrat of Rhode Island and the likely new chairman of the Armed Services Committee, said in a statement that the men and women of the National Guard “put their lives on hold to answer the call to service.”
“They will defend the U.S. Capitol with their lives,” he said, “and I trust them implicitly with mine.”
The acting defense secretary, Christopher C. Miller, said on Sunday that the F.B.I. was helping the military vet more than 25,000 National Guard members being deployed to help protect the Capitol and areas in central Washington because of potential security concerns.
All military personnel, including those in the National Guard, undergo extensive background investigations and physical examinations, including assessments of tattoos. They are continuously monitored for indications that they are involved in extremist activity and receive training to identify others around them who could be “insider threats.”
Pentagon and National Guard officials said on Tuesday that existing vetting procedures were sufficient to identify and weed out violators. “I don’t see any current change in policies,” General Hokanson said.
Lloyd J. Austin III, Mr. Biden’s pick for defense secretary, acknowledged during his confirmation hearing on Tuesday that extremists in the military were a problem and said their removal would be a priority if the Senate confirmed him. “The job of the Department of Defense is to keep America safe from our enemies,” he said. “But we can’t do that if some of those enemies lie within our own ranks.”
General Austin added later, “We can do a better job of screening the folks we bring in.”
The F.B.I. investigation into the Capitol rampage, still in its very early stages, has identified at least six suspects with military links out of the more than 100 people who have been taken into federal custody or the larger number still under investigation. They include a retired Air Force lieutenant colonel from Texas, an Army officer from North Carolina and an Army reservist from New Jersey. Another person who served in the military was shot and killed in the assault.
The military’s examination of its ranks is a turning point for the Pentagon, which has a history of downplaying the rise of white nationalism and right-wing activism, even as Germany and other countries are finding a deep strain embedded in their armed forces.
Federal officials are vetting thousands of National Guard members arriving to help secure the inauguration. Of the 25,000 Guard personnel who are in Washington, any who will be near Mr. Biden or Ms. Harris will receive additional background checks, a standard procedure to counter insider threats that was also taken before Mr. Trump’s inauguration in 2017.
In addition to the National Guard members, the Pentagon plans to deploy about 2,750 active-duty personnel in support of the event. About 2,000 of them will perform ceremonial duties in military bands, color guards and a salute-gun battery, and serve as sentries and ushers.
The remaining 750 are members assigned to specialized units dealing with chemical, biological, nuclear or radiological threats; bomb squad technicians; medical personnel (including those conducting coronavirus testing in support of the attending physician of Congress); and logistics and communications support personnel.
Coast Guard helicopters and vessels will be in the air and nearby waterways.
Air Force fighter jets stationed at Joint Base Andrews in Maryland will be aloft over the region. The air space over the Capitol, the National Mall and the rest of the city will be even more restricted than usual, Pentagon officials said.
Jennifer Steinhauer contributed reporting.