Officials are investigating an outbreak of diarrhoea in Haiti.
Reports say about 50 people have died after suffering acute fever, vomiting and diarrhoea. Many more with similar symptoms have been admitted to hospitals north of the capital.
A senior UN health official told the BBC it was not clear what caused the outbreak. Test results are due later.
The country is still suffering the aftermath of January’s quake which killed some 250,000 people.
It also left 1.5 million homeless.
An unnamed Haitian health official told AFP news agency the outbreak was cholera but the report could not be confirmed. The government was expected to make an announcement on the outbreak later on Thursday.
Jessica Du Plessis, from the UN’s humanitarian affairs agency, said the outbreak was centralised on the northern half of Haiti. She told the BBC there were about 300 people showing symptoms in a few hospitals and clinics in that area.
Many of the ill have been taken to a hospital in the town of Saint-Marc, about 100km (60 miles) north of Port-au-Prince, medical officials said.
The Pan American Health Organization (Paho) has sent two teams to the south of the Artibonite department, near Saint-Marc, a doctor with Paho told the BBC.
Little is known of the outbreak beyond “a high incidence of diarrhoea”, said Dr Michel Thieren of Paho.
“Nothing can be verified at the moment. We have no numbers, no epidemiological data,” he said.
The symptoms could be associated with a number of underlying diseases, he added.
There were fears of a cholera outbreak in the aftermath of the earthquake with many survivors forced into makeshift camps with unsanitary conditions and little access to clean drinking water, but there were no outbreaks, the World Health Organization says.
The Artibonite department was not badly damaged in the earthquake but a number of people who lost their homes took shelter there and many have not left.
Cholera is spread through people consuming water or food contaminated with cholera bacteria. The source of contamination is usually the feces of infected people.
It causes diarrhoea and vomiting leading to dehydration and can kill quickly if left untreated. It is easily treated though rehydration and antibiotics, however.