"I have seen the video which shows what appears to be a house party taking place inside a Chicago residence," Lightfoot wrote. "What was depicted on the video was reckless and utterly unacceptable."
The mayor asked citizens to anonymously call police if they see people gathering in groups and not practicing social distancing.
"While most Chicagoans are doing their part to prevent the spread of COVID-19, reckless actions like these threaten our public health and risk erasing the progress we have made. We will hold those responsible accountable," according to the mayor. "I am asking everyone to be in this together."
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She said there's "a reason we are asking you to stay home and socially distance" because "it saves lives."
The party took place in the 2000 block of North Narragansett Avenue, state Rep. LaShawn Ford told NBC Chicago.
Ford said the woman who owned the house was not home when her children threw the ill-advised bash.
"To say that they should practice social distancing because it will save your life, you should wear a face mask because it will save your life - they don't see that," Ford said. "They don't see past the next minute."