The United Nations has set up an independent panel to investigate the source of cholera in Haiti.
The move comes after accusations that UN peacekeepers from South Asia introduced the disease to the poverty-stricken country.
The UN has previously denied any connection.
More than 2,000 people have died and thousands more have been infected by cholera in Haiti since the outbreak began in October.
UN Secretary General Ban Ki-Moon said the scientific panel was necessary to "find answers that the people of Haiti deserve".
"There are several theories of the origins of the cholera outbreak in Haiti - not all reports have reached the same conclusion," he said at a news conference on Friday.
"There remain fair questions and legitimate concerns which demand the best answers that science can provide," he added.
He said the panel would be "completely independent" and have full access to UN premises and personnel.
'South Asia strain'
Nepalese peacekeepers became the object of local suspicion partly because cholera is very rare in Haiti but endemic in Nepal.
In November, the US Center for Disease Control found that the cholera strain in Haiti most closely resembled a South Asian strain.
A leaked study by epidemiologist Renaud Piarroux on behalf of the French and Haitian governments also suggested the strain had been imported from South Asia.
Sources who saw the report said it had evidence the outbreak was caused by river contamination by Nepalese troops.
But Mr Ban said that initial reports by the UN suggested that peacekeepers from Nepal were not responsible.
The Nepalese army denies the accusation, but said earlier this month that soldiers were not tested for cholera before they went.
The UN has said that health officials now estimated that 650,000 people in Haiti could become infected with cholera over the next six months.
Nearly 100,000 people in the country have already contracted the disease.