Three people have died this week in Argentina from pneumonia of unknown origin, local health authorities said on Thursday.
The mysterious respiratory illness has been reported in nine people in north-western Tucuman province, including eight medical staff at the same private clinic, and three have died since Monday, provincial Health Minister Luis Medina said.
Authorities have ruled out Covid-19, flu and influenza types A and B, and are conducting tests on the illness, Mr Medina said.
The prestigious Malbran Institute in Buenos Aires is analysing the samples.
The third victim was a female patient, 70, admitted to the same clinic where staff have been infected, before a surgical procedure.
Mr Medina said the woman could have been "patient zero, but that is being evaluated".
The first patient died on Monday and the second on Wednesday.
Mr Medina said on Wednesday the patients were suffering from "a severe respiratory condition with bilateral pneumonia … very similar to Covid".
Experts were analysing the local water and air conditioners to see if it was a case of poisoning, while Mr Medina said it could also be due to an infection.
The first six patients started showing symptoms between August 18 and 22.
Of the last three cases, two are receiving hospital treatment and one is being monitored at home.
