Ilan Naibryf attends the University of Chicago and is a member of the student board of Chabad on campus.
Richard Augustine, 77, a Chicago native, is also missing. His daughter said her father was supposed to fly to Chicago tonight for a weekend visit. He had just returned from the West Coast, Debbie Hill said, and was packing his bags to come to see her.
"He was actually supposed to fly in today," Hill said. "He just finished up a trip with my brother out in California and he went home to repack his bags and he was coming to spend the weekend here.
WATCH: Security camera video shows moment of Surfside building collapse
Hill said she got a call in the middle of the night about the collapse, and is still waiting to hear from authorities in Florida. She said she's seen video of the collapse and her father's unit is among those seen falling.
"He was right in the corner where the buildings met, so," she said. "Yeah, that was pretty scary to watch. And of course, immediately I tried to call him and his phone went straight to voicemail."
RELATED: At least 3 dead up to 99 missing in Florida building collapse
The third missing Chicagoan is Juan Mora, a Loyola University graduate student who the Miami Herald reported was visiting his parents at the time of the collapse. Juan Mora Sr. and Ana Mora, who were born in Cuba, live in Champlain Towers. All three are missing.
A wing of the 12-story building in the community of Surfside came down with a roar around 1:30 a.m. By late afternoon, nearly 100 people were still unaccounted for, authorities said, raising fears that the death toll could climb sharply. Officials did not know how many were in the tower when it fell.
Dozens of survivors were pulled out, and rescuers kept up a desperate search for more.
Teams of 10 to 12 rescuers at a time entered the rubble with dogs and other equipment, working until they grew tired from the heavy lifting, then making way for a new team, said Florida Chief Financial Officer Jimmy Patronis, the state's fire marshal.
"They're not going to stop just because of nightfall," Patronis told Miami television station WPLG. "They just may have a different path they pursue."
The seaside condo development was built in 1981. It had a few two-bedroom units on the market, with asking prices of $600,000 to $700,000.
The area has a mix of new and old apartments, houses, condominiums and hotels, with restaurants and stores serving an international combination of residents and tourists. Among the neighborhood's residents are snowbirds, Russian immigrants and Orthodox Jewish families.
Please note: The video at the top of this story is from a previous report
The Associated Press contributed to this report.