The authorities have faced criticism for underreporting the toll of Maria - the most powerful storm to hit the region in almost 90 years.
Originally, the government had set the death toll at 64, counting only direct victims of the tragedy. Some experts had claimed that the death toll actually neared 4,600. That figure was likely as low due to officials strictly classifying only certain deaths - such as those caused by collapsing buildings, flying debris, floods and drownings - as caused by the hurricane.
"This shows the magnitude of the catastrophe", Governor Rossello told El Nuevo Dia newspaper. "I make mistakes. Now, hindsight tends to be 20-20". They also said the public health system needs to be strengthened, though Goldman said they don't know yet whether those weaknesses contributed to storm-related deaths. "The government tried, but they were not prepared in both logistics and preventions".
Yulín Cruz, In an interview with the BBC, said Trump and his administration have a "ridiculous obsession" with making the federal government relief efforts "a good news story".
Cruz went on MSNBC on Wednesday shortly after Trump's comments and said the president was "incapable of feeling solidarity and empathy".
"When I saw people dying I opted to shout it".
For months after the storm, Puerto Rico's Government reported the number of lives lost at 64, now they're saying it is far worse than first reported - 2,975 lives lost.
Researchers estimated the excess deaths with the help of mathematical modeling that compared post-hurricane deaths to the expected number based on historical patterns, and adjusted for age, sex and migration from the island.
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As in many GOP races across the country, candidates in the Republican primary competed to prove their loyalty to President Trump . He took office in the state in the early 1980s, first as a congressman and then as a senator in the seat once held by Goldwater.
What does the report say?
The latest Puerto Rico figure was derived from comparisons between predicted mortality under normal circumstances and deaths documented after the storm, a number that turned out to be 22 percent higher. About 8 per cent of the total 3.3 million people have left the island.
The mayor of San Juan, Puerto Rico, slammed President Donald Trump on Wednesday after he said his administration did a "fantastic job" in helping the US territory Rico recover from last year's devastating Hurricane Maria.
The governor said he would sign an executive order to create a committee to examine and put into practice the report's recommendations.
Rescue workers come to the rescue after Hurricane Maria.
In the three months after the hurricane, there were 1,427 more deaths than the average for the same period over the previous four years, according to the report by the Milken Institute.
The new study raises questions about President Trump's response to the disaster.