Nobody was seriously injured, although several inmates and employees were treated for smoke inhalation. Nobody was taken to a hospital, said Ignatius Carroll, a Miami Fire Rescue spokesman.
About 30 inmates from the third floor were taken to another section of the jail after smoke enveloped the general population area, said Carroll and Jannelle Hall, a spokeswoman for the Miami-Dade Corrections Department.
''They were evacuated within the facilty,'' Hall said. ``They weren't taken outside.'
She said flames were seen on two floors and smoke on four floors, including one with administrative offices.
Fire investigators were still trying to determine the cause of the blaze, she said.
''They are looking at possibly an area in the laundry room where perhaps something could have been started or accumulated over a period of time,'' she said.
Carroll said it may have been an ''exhaust fan malfunction'' on the seventh floor.
Said Hall: ``It's an old building. In old buildings anything can happen.''