Latest estimates put the figure at more than 900 in the two countries but many more are missing and thousands have been left stranded as rain continues to fall.
Christina Estrada of the Red Cross based in the Dominican Republic, said it was too early to say exactly how many people have been killed and left homeless.
Meanwhile, an international relief operation is gathering pace.
In Haiti, emergency relief teams are still struggling to get to the worst-hit villages in the south that are immersed in deep water.
Many flood-hit towns are impossible to reach except from the air. And continuing rain has hampered the access even of helicopters.
John Bevan, senior humanitarian officer for the United Nations in Haiti, told BBC Caribbean Service that while helicopters had managed to reach the border town of Fonds Verrettes, low cloud cover over the south-eastern town of Mapou made the situation there difficult.
“It’s difficult to get access to see how many people are affected and where they are. The main fear now is epidemic.”
“We are still in the evaluation and emergency assistance phase and it will be a while until we start any sort of rehabilitation,” Mr Bevan said.
The 15-member Caribbean Community, Caricom, is preparing to provide disaster relief to flood-hit Haiti, through the Caribbean Disaster Emergency Response Agency (CDERA).
Deputy Caricom Secretary General, Ambassador Lolita Applewhaite said Caricom and CDERA were working with Haitian authorities to provide disaster relief.
But Ms Applewhaite could not say what types of assistance would be provided.
“We are in touch with Haiti to ascertain what the needs are and we’ll be moving very quickly to lend whatever assistance we can,” Ms Applewhaite said.
The two organisations have also said they would also be willing to assist the Dominican Republic, if they receive a request.
Aid agencies have said the relief operation is only just beginning and will have to go on for months.
Two teams from the United Nations Development Programme, arrived on the island on Friday to evaluate the situation and the needs on the ground
The UN says that 1, 500 people are feared dead or missing in Haiti, and that number could rise.
“We believe there are more than a total of 48,000 people affected in the two countries,” said Elisabeth Byrs, a Geneva-based spokeswoman for the UN Office for the Co-ordination of Humanitarian Affairs.
Over the border, disinfectant is to be sprayed in the hardest-hit Dominican Republic town of Jimani, to stop the spread of disease.
The US ambassador, Hans Hatler, toured the stricken town, announcing $50,000 in aid.
Dominican President Hipolito Mejia has also been to the scene and said he was happy with international relief efforts.
Nearly 700 Red Cross volunteers were reportedly in the town, helping those injured and putting up mosquito nets to protect against outbreaks of malaria and dengue fever.