The corona virus, influenza A and B flu viruses and hantaviruses have already been ruled out as causes: in Argentina three people died of “pneumonia of unknown cause”.

As the health minister of the northwestern province of Tucumán, Luis Medina Ruiz, announced on Thursday, the nine cases of the respiratory disease were found in a private clinic. Eight of the sick are or were nurses at the clinic, which is located in the city of San Miguel. Three of those infected have died since Monday.

According to the information, they are two nurses and a 70-year-old patient who had been admitted to the clinic for an operation.

The health authorities are now trying to find out which pathogen triggers the pneumonia. As the “Buenos Aires Times” reports, it is a double-sided pneumonia in which both wings of the lungs are affected. There have been no new cases since August 22, and the facility is being strictly isolated, it said.

On Wednesday, the Minister of Health said that in addition to a pathogen, possible “toxic” and “environmental causes” would also be checked. The water and air conditioning systems, for example, are now also being examined.