The City of Miami tweeted that people in a building facing the crane should try to take shelter on "the opposite side" of the building or in a stairwell.
Some two dozen other cranes in the city were still upright, Alfonso said.
"We have no reported injuries", Alfonso said.
The City of Miami has warned its citizens that the huge construction cranes that dot the skyline could cause potentially deadly accidents in Hurricane Irma.
Hurricane Irma snaps a crane in two as it rips through downtown Miami
The cranes were thought to be able to withstand the direct hit of a Category 4 hurricane, however, Irma's winds in Miami are just at the Category 1 level.
They could not be moved ahead of Irma because the massive equipment, with counterbalances weighing up to 30,000 pounds, is a slow process that would take about two weeks to complete, according to city officials.
Although Irma's eye was almost 100 miles from the Miami area, hurricane-force wind gusts battered the area on Sunday. "We will have a crew over to secure the crane as soon as the weather permits". Gusts over 90 miles per hour (145 kph) were reported at Miami International Airport. People also posted pictures of the cranes. With its strong wind gusts ravaging the city, officials have been warning there could be more damage with similar incidents given the area's building boom and intensifying conditions.
Meantime, officials from Broward County report that a man fell to his death from a nine-story building while boarding up windows.