Up to 200 members of the National Guard on duty in Washington DC for inauguration day have tested positive for coronavirus, an official has said.
More than 25,000 troops were drafted in from all over the US to ensure a smooth transition of power.
An official who spoke to Reuters on condition of anonymity said that although some troops had become infected – it was less than 1% of the total number working across the Capitol.
Huge numbers were deployed to Washington for Joe Biden’s inauguration following the riots and looting of Capitol buildings on 6 January.
Former president Donald Trump now faces an impeachment trial after he rallied his supporters to march to the White House.
According to the latest reports there are just 10,500 National Guard troops still on duty, with 15,000 due to return to their home states in the next five to 10 days.
Around 7,000 are expected to remain until at least the end of the month, with 5,000 still there by mid-March, officials have said.
More from Covid-19
COVID-19: Crowds at Heathrow Airport spark social distancing concerns
COVID-19: Scientists warn against early easing of lockdown as PM warns of ‘more deadly’ coronavirus variant
COVID-19: AstraZeneca to cut COVID-19 vaccine delivery to EU by 60%, reports
COVID-19: Matt Hancock says South African variant could reduce vaccine efficacy by half
COVID-19: Concerns grow over number of carers turning down vaccine
COVID-19: UK’s ‘more deadly’ new variant is another cruel twist in the pandemic
It comes as pictures of troops forced to sleep in a parking garage on their breaks in Washington sparked outrage in Congress.
On Friday morning the president expressed his dismay that troops had been denied a place to rest in a conversation with General Daniel R Hokanson, chief of the National Guard.
There are now calls for an investigation.
White House press secretary Jen Psaki thanked the Guard for all their help following the events of 6 January and offered them assistance if they needed anything.