But Alfonso said the city was doing far better than expected when Irma was forecast to slam straight into Miami.
The crane collapsed and fell into the top of a building under construction, said Miami City Manager Daniel Alfonso.
Emergency personnel were unable to respond because of high winds, Miami-Dade County Director of Communications Mike Hernandez said.
The images of a crane toppled over a high rise flooded social media as Irma landed on the southern tip of Florida's coast September 10. "Taking them is not something you can easily do".
Irma is forecast to make landfall in southern Florida early Sunday and pass west of Miami, with sustained winds at or above 145 mph; its hurricane-force winds extend up to 70 miles from its center. She told The Associated Press that from her 14th floor apartment, she saw the crane toppled over where it hit another building.
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More than two dozen cranes hang over residents' heads with horizontal arms of the tall tower devices hanging loose as they could not be tied down or moved in preparation for Irma. The expanded evacuation area also includes Homestead, Coral Gables, South Miami, Miami Shores and North Miami Beach.
A second crane collapse was later reported at a building under construction on Northeast 30th Terrace.
The arms of the tower cranes are left unlocked during storms, allowing them to swing around and follow the wind, much like a weather vane.
"Hurricane winds are blowing in one direction but a tornado could twist things, and nothing can be created to withstand the tornado effect", Whiteman said.