A supporter of Aida Flores pulled the microphone away and handed it over to Flores, who then made unfounded claims of voter suppression.
Election results show that Sigcho-Lopez defeated Flores with 53% of the vote.
Immigrant rights activist Elvira Arellano tried to shout down Flores, eventually grabbing the microphone back.
The Chicago Board of Elections could not comment on Flores' allegations, but said in a written statement: "The Cook County State's Attorney's Office has a hotline where any person can lodge complaints concerning fraud or voter intimidation. Any election judge who feels they have been unreasonably intimidated or threatened in any way related to elections may contact the SAO Election Fraud hotline at 773-674-3311 or SAO.ElectionFraud@CookCounty.onmicrosoft.com."