United Nations investigators have taken samples of foul-smelling waste trickling behind a Nepalese peacekeeping base in Haiti amid claims that sewage from the newly arrived unit caused the cholera epidemic that has made more than 4,000 people ill.
Journalists visiting the base unannounced came upon the investigators and mission spokesman Vincenzo Pugliese later confirmed that the military team was testing for cholera.
It was the first public acknowledgement that the 12,000-member force was directly investigating allegations that its base played a role in the outbreak.
Meanwhile, the epidemic continued to spread, with cases confirmed in two new departments in Haiti's north and north east, said UN Office for the Co-ordination of Humanitarian Affairs spokeswoman Imogen Wall. At least 303 people have died and 4,722 have been taken to hospital.
International aid workers and the United Nations are focusing their efforts on stemming the spread of the outbreak, which was first noted on October 20. But Haitians are increasingly turning their attention to its origins - how did a disease which has not been seen in Haiti since the early 20th century suddenly erupt in the countryside?
The mission strongly denies its base was a cause of the infection. Mr Pugliese said civilian engineers collected samples from the base on Friday which tested negative for cholera and the mission's military force commander had ordered the additional tests to confirm.
He said no members of the Nepalese battalion, whose current members arrived in early October for a six-month rotation, had the disease.
The unit's commander declined to comment.
Local politicians including a senator and the mayor of Mirebalais are pointing the finger at the Nepalese peacekeeping base, perched above a source of the Meille River, a tributary to the Artibonite River on Haiti's central plateau.
The Artibonite River has been the source of most infections, which remain concentrated in the rural area surrounding it - mostly down river from the mouth of the Meille.