All the patients died at Nazareth House Nursing Home in Fahan as a result of a respiratory type illness.
The HSE has confirmed the deaths have occurred in between the 22nd March and the 2nd April 2012.
Five of these deaths occurred in a cluster over the past five days.
“The HSE is fully investigating the matter and all appropriate treatment and control measures have been put in place.
“All residents in the nursing home are currently receiving either active or preventative treatment,” said a statement.
Dr Peter Wright, Director of Public Health, HSE North West said “The Public Health Department in HSE North West is closely managing and monitoring the situation.
“Respiratory illness is a common cause of death in older people. The Public Health team will work closely with the Nursing Home management to determine the nature of the illness.
“Samples have been sent to the National Viral Reference Laboratory for determination.”
The HSE’s Public Health Departments has requested that GPs report unusual clusters of respiratory illness.
It’s understood tests have been carried out which have ruled out a bacterial infection as the cause of the deaths.
Experts are now investigating if the deaths were possibly caused by a strain of influenza.