Within a span of about 24 hours, three House Democrats announced they had tested positive for COVID-19, prompting concern that last week's Capitol siege had turned into a super-spreader event.
Those who tested positive were among dozens of politicians who were whisked to a secure location when pro-Trump insurrectionists stormed the Capitol on Wednesday.
It is not certain where and when the three caught the illness, but the Capitol's attending physician notified all House members of possible virus exposure and urged them to be tested.
Doctor Brian Moynihan said members who were in protective isolation last Wednesday "may have been exposed to another occupant with coronavirus infection".
Congressman Brad Schneider said on Twitter that he tested positive Tuesday morning.
He said he was not feeling symptoms but he expressed dismay at the spate of positive test results and blamed Republican members of Congress who declined to wear masks when they were offered during the lockdown.
"Today, I am now in strict isolation, worried that I have risked my wife's health and angry at the selfishness and arrogance of the anti-maskers who put their own contempt and disregard for decency ahead of the health and safety of their colleagues and our staff," Mr Schneider said.
Mr Schneider's comments came a few hours after similar remarks from Congresswoman Pramila Jayapal, who said she had tested positive and criticized GOP members of Congress.
"Only hours after President Trump incited a deadly assault on our Capitol, our country, and our democracy, many Republicans still refused to take the bare minimum COVID-19 precaution and simply wear a damn mask in a crowded room during a pandemic."
Republican Bonnie Watson Coleman of New Jersey said on Monday that she had tested positive for COVID-19.
They were among dozens of politicians whisked to a secure location when pro-Trump insurrectionists stormed the Capitol.
Some members of Congress huddled for hours in the large room, while others were there for a shorter period.
Within hours of their announcements, Republicans Debbie Dingell and Anthony Brown introduced legislation that would impose a $1,000 fine on any member of Congress refusing to wear a mask on Capitol grounds during the COVID-19 pandemic.
Ms Jayapal also called on the House sergeant at arms to remove any House member who declined to wear a mask from the floor.
"This is not a joke. Our lives and our livelihoods are at risk, and anyone who refuses to wear a mask should be fully held accountable for endangering our lives because of their selfish idiocy," she said.
Mr Schneider said he was in the crowded secure location for about four hours.
He said he received the first dose of a COVID-19 vaccine a few days before that potential exposure.
However, health experts noted that it was possible for a person to get infected with the virus just after vaccination because the vaccine did not have enough time to provide protection.
"I don't know from whom I got this virus, or even necessarily if I got it in that room," he said during a virtual news conference from his suburban Chicago home, where he was isolating.
"But I know that my exposure in that room was greater than at any other time through this entire pandemic."
Over the weekend, the Capitol's attending physician notified all House members of possible virus exposure and urged them to be tested.