US health authorities say the cholera strain that has killed more than 330 people in Haiti most closely resembles a South Asian strain.
The US Centers for Disease Control found that Haitian cholera patients had all been infected with the same strain.
The United Nations is investigating allegations that excrement from Nepalese peacekeepers caused the epidemic, the BBC reports.
Haitian Health Minister Alex Larsen says the outbreak was unlikely to have originated in his country, though he admits it's unlikely the origin will ever be known.
"Although these results indicate that the strain is non-Haitian, cholera strains may move between different areas due to global travel and trade," he said, according to Agence France-Presse.
He added that the strain was probably transmitted by contaminated food or water, or an infected person.
Cholera endemic in Nepal
The Nepalese camp has become the object of local suspicion partly because cholera is very rare in Haiti but endemic in Nepal.
The UN said last week that tests taken from the peacekeepers' camp and adjacent waters were found to be negative, but it's now investigating further.
Poor sanitary conditions make the camps and slums where many are living after the country's January earthquake vulnerable to cholera, which is caused by bacteria transmitted through contaminated water or food.
Some 1.3 million survivors of the devastating quake are living in tent camps in and around the capital.
Health experts say they expect that the outbreak will soon diminish but that the disease will eventually join malaria and tuberculosis in becoming endemic in Haiti.