Three million Florida residents were urged to leave their homes

Parts of the state's central Atlantic coast were devastated after Jeanne made landfall on Saturday night with 120mph (160km/h) gusts.

At least six people were killed and two million were left without electricity.

It has now weakened but has threatened to spawn tornadoes in the states of Georgia and North Carolina.

Jeanne's victims included a 15-year-old boy in Clay County, south of Jacksonville, who died after a tree fell on him, the Associated Press reported.

Earlier, Jeanne battered the Bahamas with violent winds, sending hundreds of people fleeing to emergency shelters.

Jeanne's destructive power was already clear from the devastation in Haiti, where more than 1,500 were killed in flooding and landslides.

There is still a month of the hurricane season left.

'Life and death'

The hurricane, a dangerous category three storm, came ashore near Stuart, Fort Pierce and Vero Beach on Florida's east coast - the same region battered by Hurricane Frances three weeks ago.

Everyone in Florida is fed up. Jeanne is expected to hit Broward where I live very hard but I've noticed that people are not taking this seriously Chrissybil Boulin, Pembrook Pines Jeanne: Your experiences Back-to-back hurricanes

Florida's Governor Jeb Bush said the hardest-hit areas were Martin, Indian River and St Lucie counties on the state's central Atlantic coast.

However, the governor added that "just about everybody's been impacted by the storm in one way or the other".

As the wind and rain died down, emergency teams began assessing the damage and searching for potential victims of the storm.

"Today, the focus is on life and death. We need to get in there and find out what the situation is as soon as we can," Florida emergency co-ordinator Mike DeLorenzo was quoted as saying by Reuters.

In Stuart, a few houses and businesses have been badly damaged, but Jeanne seems to have spared the town the devastation of previous storms, the BBC's Daniel Lak reports from the town.

By 1800 GMT on Monday, the storm had weakened to a tropical depression, the National Hurricane Center said.

However, the Center warned that Jeanne could trigger tornadoes in parts of North Carolina and Georgia and could drop four to eight inches (10cm to 20cm) more rain.

Stunned disbelief

It is too early to assess the damage, but the cumulative effect of Florida's four hurricanes will be immense, our correspondent says.

Insurance claims were already expected to be in excess of $20bn, without factoring in the damage from Jeanne.

The hurricanes have so far caused at least 70 deaths in Florida.

State authorities said more than 31,000 people had taken to shelters before the storm crashed ashore, many of them people whose homes had been damaged by Frances.

No other state has been hit by four hurricanes in the same season since Texas more than a century ago.

Florida resident George Robertson-Burnett told BBC News Online: "There is a stunned sort of disbelief that this can be happening.

"Never in living memory... has there been a sequence of hurricanes to match what is now happening."