SAN JUAN, Puerto Rico (CBSNewYork/CBSNews/AP) – A Harvard University study found the death toll from Hurricane Maria last year was dramatically larger than reported.

The new study, published in the New England Journal of Medicine, estimates more than 4,600 people died in Puerto Rico, mostly because of problems accessing medicine or medical care. The official government death toll was just 64.

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Researchers knocked on doors and surveyed more than 3,000 homes across the island. They found the mortality rate increased 62 percent in the three months after the hurricane, compared to that period the year before.

They concluded the final death toll could be as high as 8,500.

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“One third of our deaths were reported because lack of medical treatment,” Domingo Marques, lead author of the study, told CBS News.

Researchers called the government’s count of 64 deaths a “substantial underestimate.”

It’s the latest study to analyze how many people died during or after the Category 4 storm that hit the U.S. territory in September 2017, causing more than an estimated $100 billion in damage. Maria caused the longest blackout in U.S. history, leaving the entire island of 3.3 million people without power, including those in hospitals and nursing homes who relied on respirators.

One of the researchers, Rafael Irizarry of Harvard University, told the AP that the estimate is uncertain because of its limited size, but that the study still provides valuable information, including how some people died.

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Photos: Hurricane Maria Batters Puerto Rico

Previous studies have found that the number of direct and indirect hurricane-related deaths in Puerto Rico is higher than the official toll, including a 2017 report that there were nearly 500 more deaths than usual on the island in September.

In late February, Puerto Rico’s governor announced that a team of experts at George Washington University would lead an independent review to determine the number of deaths caused by Hurricane Maria amid ongoing accusations that the government undercounted the toll. A preliminary report was due in May, but Puerto Rico officials announced last week that the team requested and was granted more time. The director of that study did not return messages for comment.

The government of Puerto Rico issued a statement Tuesday in response to the study saying that it welcomed the research and would analyze it.

“As the world knows, the magnitude of this tragic disaster caused by Hurricane Maria resulted in many fatalities.  We have always expected the number to be higher than what was previously reported,” said Carlos Mercader, executive director of Puerto Rico’s Federal Affairs Administration.

Puerto Rico’s Gov. Ricardo Rosselló, who is a scientist, seemed blindsided by the Harvard study, CBS News reported. His government wasn’t involved and he didn’t know it was being released.

“We welcome all studies,” Rosselló said at a press conference Tuesday. “We want the real number to come out. We had a protocol that really was subpar and we recognize it.”

During his visit to Puerto Rico last October, President Donald Trump hailed the low death toll, which at the time was 16. He compared it to Hurricane Katrina. In light of the Harvard report, a White House spokesperson said the people of Puerto Rico deserve nothing less than transparency and accountability.

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