The Mater insists it's met all legal requirements to report infectious diseases.
These 244 cases were only reported to the Health Protection Surveillance Centre in one batch yesterday.
The Mater in Dublin has been confirmed as the hospital the cases relate to.
The HSE says it's not in a position to confirm if the hospital did or didn't report the cases - and that the mater is under review.
The Mater says it's reported all positive test results to the relevant authorities on a daily basis.
It insists the Mater has at all times provided correct and up to date information required by the HSE - and that it's working with the executive to understand why that data mightn't have been accurately captured.
The cases not reported are believed to relate to staff members - the mater says comprehensive contact tracing has been carried out on all of the more than 300 staff who've tested positive.
Earlier, the Health Minister said checks would be needed to see if the matter is criminal.
The Mater says it's met all legal requirements to report infectious diseases.