The fire broke out in a cell around 3 p.m. in Division 9 of the jail, according to the sheriff's office.
Staff members quickly extinguished it, but three of them went to the hospital for smoke inhalation. Two others were seen by onsite medical staff, officials said.
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One person assigned to the cell is being evaluated.
Sheriff's office officials said the fire was not near Jussie Smollett's cell.
The cause of the fire is under investigation.