A three-week-old cholera epidemic that has killed more than 640 people in Haiti continues to spread in the slums of Port-au-Prince and in Gonaives.

The city's mayor, Pierrelus Saint-Justin, said he had personally buried 31 people and had another 15 bodies in a truck waiting for burial.

But despite the increasing number of cases, officials with the United Nations Stabilization Mission in Haiti (MINUSTAH) announced the reopening of the Dominican Republic's border with Haiti after it had been briefly sealed recently due to cholera concerns.

"During the first days, there was some closure of the border, there was some trying to examine - to filter the people who would go to the other side. It was a little bit of confusion as to what policy had to be established, but finally, the Dominican government - as far as I know - decided to open the land, the border," said MINUSTAH spokesman, Vicenzo Pugliese.

Meanwhile, sick Haitians continue to flood clinics in the Port-au-Prince slum of Cite Soleil.

Cholera, a diarrheal disease transmitted by contaminated water, has mostly hit Haiti's rural central regions so far. But authorities say it has now gained a foothold in Port-au-Prince and is menacing crowded slum areas of the capital.

Among the most vulnerable areas are tent and tarpaulin camps in Port-au-Prince still housing more than 1.3 million survivors of Haiti's devastating Jan. 12 earthquake in January.

The most recent figures issued by Haiti's health ministry said cholera had killed 648 people and infected 9,971 others.