Firefighters have evacuated 115 people from the nursing home, the Rehabilitation Center at Hollywood Hills.
Footage from the scene on Wednesday morning showed patients being rolled out of the nursing home on stretchers and taken to Memorial Regional Hospital.
The Rehabilitation Center at Hollywood Hills has a health inspection rating of "much below average" by the Florida Agency for Healthcare Administration, which evaluates all long-term care facilities in the state for the USA government.
Some residents were evacuated on early Sunday morning and some woke up feeling sick at the center, which had been without air conditioning, Broward County Mayor Barbara Sharief said.
Police have started a criminal investigation into the deaths.
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The Centers for Medicare and Medicaid Services, which regulates nursing homes, gives the Hollywood center a below-average rating, two stars on its five-star scale.
Geane Mitchell, a nurse at the centre told the WSVN news channel, she was due to begin work at 7am, having been off for the last few days.
"We came here, leaving everything at home, and we go back to nothing", Lopez said.
Aside from the nursing home deaths, at least 13 people in Florida were killed in Irma-related circumstances, many of them well after the storm had passed.
The number of deaths blamed on Irma in Florida climbed to 13 with the carbon monoxide deaths, in addition to four in SC and two in Georgia.
The number of people without electricity in the steamy late-summer heat dropped to 9.5 million - just under half of Florida's population.
~150 of Florida's almost 700 nursing facilities do not have power restored, according to the Florida Health Care Association advocacy group. Two others died after reaching hospital. "As with millions of other Floridians, our centers are coping with the loss of power and infrastructure in the communities that were most affected by the devastation", the statement reads. She said her sister could not talk or walk. The association added that it is working with state officials to identify homes without power so that utility companies could prioritize those in greatest need.