Two high-rise construction cranes toppled over in downtown Miami on Sunday as intense gusts from Hurricane Irma lashed the city.

City Manager Daniel Alfonso said in both cases, the most dangerous part of the crane — the heavy counter-balance that keeps the cranes balanced — fell straight into the construction sites.

In the first case, which happened Sunday morning, the arm of the crane also collapsed, falling onto the top level of the building. In the second case, which happened later Sunday as Irma's outer bands continued whipping throughout Miami, the arm of the crane was left dangling and threatening to fall at any moment.

Both sites had been evacuated before the storm.

"We have no reported injuries," Alfonso said.

Alfonso said city officials contacted the management of nearby residential buildings and called residents there by using a reverse 911 system to urge them to stay away from their windows in case shards of the cranes are picked up by the wind.

The incidents highlight one of the biggest concerns for Miami residents heading into the storm. The city is in the midst of a building boom, with glass-covered, high-rise condos springing up all over the heart of the city. That has left the Miami skyline dotted with construction cranes that were not taken down before the storm.

Maurice Pons, deputy director of the Miami building department, warned last week that roughly two dozen cranes were a serious threat to residents living next door.

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. That decreases the pressure on the arms.

But Pons said the cranes are designed to withstand winds up to 145 mph, meaning some could fall if Irma made a direct hit on Miami.

Irma changed course in recent days, making landfall about 100 miles southwest on Cudjoe Key and leaving the southwest corner of the state preparing for the worst. But Irma is such a massive storm that tropical- and hurricane-force winds were lashing South Florida throughout Sunday.

Social media posts showed areas of downtown completely under water, with main roads resembling white-water rivers. People also posted pictures of the cranes.

PHOTOS: Hurricane Irma makes landfall in Florida

Alfonso said things looked relatively calm by midday Sunday. A half-million homes were without power in Miami-Dade County and heavy flooding was a problem in some areas.

But Alfonso said the city was doing far better than expected when Irma was forecast to slam straight into Miami. The city even welcomed its first hurricane baby, when a mother delivered a girl in her home in Little Haiti with coaching from emergency responders over the phone.

Alfonso said there were no reported injuries or deaths so far from the storm.

"Overall, we're faring fairly well considering what was coming," he said.