MIAMI, the United States, Sept. 10 (Xinhua) -- Hurricane Irma on Sunday morning made landfall with a maximum sustained wind speed of 215 kph in Florida Keys, a coral cay archipelago located off the southern coast of Florida, according to the National Hurricane Center (NHC).

The hurricane, which arrived in Florida as a Category 4 storm, the second highest level on the five-step Saffir-Simpson scale, weakened to a Category 2 with a maximum sustained wind speed of 177 kph by afternoon as it marched up the state's west coast.

Still, many areas in Florida have been affected by the hurricane, which killed at least 27 people when it hit the Caribbean.

The death toll is expected to rise as the path of the hurricane is projected to cross ill-prepared population centers in west Florida.

"Once this system passes through, it's going to be a race to save lives and sustain lives," U.S. Federal Emergency Management Agency chief Brock Long told "Fox News Sunday."

Forecasters warned that the entire state -- including the Miami metropolitan area of 6 million people -- was in danger because of the sheer size of the storm.

Much of downtown Miami has been flooded due to the storm surge, and two construction cranes have also been broken.

TV signals have been completely cut off since early morning and the power went out shortly after.

Local media reported that more than 2 million people are out of power in the state of Florida, including three quarters of the Miami-Dade County located in southeast of Florida. Utility officials said it will take weeks to restore electricity to everyone.

Local police imposed a curfew starting 7 p.m. (2300 GMT) Saturday until 7 a.m (1100 GMT) Sunday, and said police and the fire department will not respond to calls after the wind speed reaches 39 mph, or 63 kph.

After leaving Florida, a weakened Irma is expected to push into Georgia, Alabama, Mississippi, Tennessee and beyond. A tropical storm warning was issued for the first time in Atlanta, more than 300 km from the sea coast.

A White House statement said U.S. President Donald Trump is closely monitoring the situation in Florida, and will travel to the state "very soon."

"I hope there aren't too many people in that path," Trump said of Hurricane Irma. "We tried to warn everybody. That's a bad path to be in."