Hurricane Isaac has weakened to a tropical storm but has continued on its path of devastation, bringing strong winds, taking down trees, and causing extensive flooding across Louisiana.

Nearly half of Louisiana has been left without power, equating to more than 900,000 homes and businesses. Some areas could be without power for up to week as extensive works will be required to restore power to various regions.

Another 150,000 people have been left without power in Mississippi, although work is already ongoing to bring back power to those suffering outages there.

Although New Orleans got away relatively lightly from Isaac compared to Hurricane Katrina seven years ago, the areas to the north and south of New Orleans have suffered terribly. Many who lived through Katrina have been left stunned at the speed at which flood waters have risen, and thousands have had to be evacuated and rescued.

Lt Gov Jay Dardenne said the floodwaters were "shockingly fast-rising, from what I understand from talking to people. It caught everybody by surprise."

Meanwhile Louisiana officials are calling for residents to evacuate after Isaac damaged a large dam, with fears now that the dam could collapse completely.

The Lake Tangipahoa Dam is intact but has been barraged by the storm and huge amounts of water that came along with it. Officials fear the damage may cause even more water to spill into the full river and create danger for the 50,000 residents who live downstream of the dam, located about 100 miles north of New Orleans.

Louisiana Gov. Bobby Jindal has called for buses to go into the area and assist with evacuating the residents who may be in danger of flooding, according to Tangipahoa Parish President Gordon Burgess.

The evacuations and other rescue missions are being helped along by the National Guard. Gov. Jindal called all of Louisiana's Guardsmen into action on Wednesday, and other servicemen and -women from neighboring states bring the total number of the force in Louisiana to about 8,000.

Early Thursday Isaac continued on its path northwards and targeted Baton Rouge, Louisiana. Tropical Storm Isaac will continue to move over Louisiana over the course of Thursday, according to the U.S. National Hurricane Center (NHC), and Arkansas and Missouri will be next up to be hit by Isaac as it continues its northwards path.

The NHC has warned that despite its winds weakening, Isaac still poses a threat to life, and residents still within its path should exercise extreme caution. Strong storm surges, floods, and isolated tornadoes are still highly likely, according to the NHC.