(Reuters) - New York state's health department may have undercounted the COVID-19 death toll in state nursing home residents by as much as 50%, according to a report released by the state attorney general's office on Thursday.

The report, issued while the state prosecutor's office continues to investigate nursing homes' response to the COVID-19 pandemic, indicated that some facilities underreported deaths to the state health department. It also found that the health department did not count the deaths of nursing home residents who were transferred to and died in hospitals in some cases.

"As the pandemic and our investigations continue, it is imperative that we understand why the residents of nursing homes in New York unnecessarily suffered at such an alarming rate," New York Attorney General Letitia James said in a statement.

The report sheds light on several errors in the state's COVID-19 response in nursing homes, for which Governor Andrew Cuomo has been criticized since the spring, when New York was the epicenter of the U.S. COVID epidemic.

Cuomo's administration came under fire in particular for guidance it issued on March 25, saying nursing homes could not deny entry to COVID or suspected-COVID patients.

That guidance was rescinded through an executive order in May, but the attorney general's report found that it "may have led to an increased risk of fatalities in some facilities" where the disease spread like wildfire.

A representative for Cuomo did not immediately respond to a request for comment.

New York has recorded the most COVID-19 deaths of any state with more than 32,000, according to Reuters' data.

The New York Department of Health reported 6,423 nursing home resident deaths due to COVID-19 from March through August 3, based on reports from 619 nursing homes, though that number could be as much as 50% lower than the reality, the attorney general's report said.

It also found that "nursing homes' lack of compliance with infection control protocols put residents at increased risk of harm," as in cases where COVID-positive residents were not sufficiently isolated to curb viral spread.

When the prosecutor's office investigated a sampling of 62 nursing homes, it found large discrepancies in the death count data it received compared to the data reported to the Department of Health.

In one case, the report said, "a facility reported five confirmed and six presumed COVID-19 deaths at the facility as of August 3 to DOH. However, the facility reported to OAG a total of 27 COVID-19 deaths at the facility and 13 hospital deaths - a discrepancy of 29 deaths."

The report said the attorney general's office was investigating those data discrepancies that "cannot reasonably be accounted for by error or the difference in the question posed."

(Reporting by Gabriella Borter; Editing by Mark Heinrich)