The death toll rose from four to seven on Sunday as investigators searched through the charred remains of the three-story building in Cicero for victims and residents waited anxiously to hear word of their loved ones and neighbours.
"To happen on a day when families are usually coming together for love and life -- Valentine's Day -- it makes it even more tragic," said town spokesman Ray Hanania. "It impacted everybody, including the firemen."
He said initial reports indicated the victims may have been related.
It was unclear how many people had lived in the building, making it difficult to account for residents.
Hanania estimated the number of residents was anywhere from 23 to 40 people. The building had two and three bedroom apartments.
The fire appeared to have started in the building's attic, Hanania said, adding that the victims may have lived in the attic and on the second floor.
Authorities did not immediately release the victims' identities, but said a 20-year-old male, a 19-year-old female, an 18-year-old female and a set of 16-year-old twins -- a brother and sister -- were among the victims.
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