Hanna left many parts of Haiti submerged in flood waters, and the country's president, Rene Preval, spoke of a "catastrophe." The storm also cut off power supplies in the southern Bahamas on Wednesday and swept across Cuba and Puerto Rico.
The death toll in Haiti is expected to rise, and the country's president has compared the disaster to Hurricane Jeanne, which claimed over 3,000 lives in 2004.
More than 100 people have been killed by storms in Haiti in the last three weeks.
Hanna is forecast to hit the central and northern Bahamas on Thursday, before transforming into a hurricane with winds of at least 74 mph (119 kph). It is expected to reach the U.S. coast near the border of North Carolina-Virginia on Saturday.
Hurricane Ike and Tropical Storm Josephine are close behind Hanna, although it is not yet clear if they will reach land.
Hanna comes in the wake of Hurricane Gustav, which hit New Orleans on Monday prompting the evacuation of some 2 million people from the city. Despite the city's mayor calling the then-approaching Gustav "the storm of the century," the hurricane was not as powerful as Hurricane Katrina, which devastated the city in 2005, killing more than 1,500 people.
Residents of New Orleans have begun to return home after the evacuation.
