Florida Governor Rick Scott on Monday warned the path to recovery from Irma would be long and hard, particularly for the worst-hit Keys island chain that bore the brunt of the storm's destructive force.

"There's devastation," Scott told a press conference following an aerial tour of the archipelago, which was the first part of the United States to be struck by Irma while it was still a Category Four hurricane.

"I just hope everybody survived," he said. "It's horrible what we saw. Especially for the Keys, it's going to be a long road.

"We saw a lot of boats washed ashore and we saw any, basically, any trailer park there overturned," Scott continued, adding that water, sewage and electricity had all been knocked out.

Footage from the Grassy Key island shot by US broadcaster NBC showed downed power lines, felled trees, and streets strewn with debris and vehicles. But homes that were made from concrete appeared to have withstood the gusts.

Most Keys residents had followed mandatory evacuation orders, but there were some holdouts who had to hunker down as Irma tore over the area known for its fishing and scuba diving.

The US military was deploying air search and rescue missions as well as two amphibious warships in addition to the aircraft carrier the USS Abraham Lincoln which arrived there Sunday night.

As of Monday the storm had weakened to a depression, with wind speeds of 60 miles per hour (95 kilometers per hour), but it continued to threaten northern parts of the state with flooding.

Scott told the more than six million citizens who fled its path -- in one of the biggest mass evacuations of US history -- they should wait until authorities had restored power and cleared debris before returning home

"Don't think just because this has passed you can run home. We have downed power lines all across the state. We have roads that are impassable.

"Our goal is don't put any more lives at risk," he said, adding that the current major threat is flooding in the northern part of the state.

The city of Jacksonville, population 880,000, in northeast Florida ordered urgent evacuations Monday as record floods were set to rise even higher with the afternoon's high tide.

But when it came to the west coast of the peninsula, the storm was not as destructive as some had originally feared, Scott said.

"I didn't see the damage I thought I would see," he reported. "This is confirmed to the mayors I've spoken to today, it's not as bad as we thought."

The death toll from Irma currently stands at 40, mainly from the Caribbean. Florida officials Monday said two people were killed in the state.

Source: AFP