Devastation caused by Hurricane Maria in Puerto Rico last September saw 4,645 people die, despite the official government death toll standing at just 64.

The shocking news about the storm, which also caused $90 billion in damage, was revealed in a new Harvard study released today.

Published in the New England Journal of Medicine, it found that in the weeks following the storm, there was severe disruption to health-care for the elderly and basic utility services for the chronically ill - leading to more deaths.

However, as of December 29, the Department of Public Safety had certified just 64 deaths from the hurricane.

A new report has revealed that at least 4,645 people died when Hurricane Maria hit Puerto Rico, despite an official government death toll of just 64

The study saw researchers interview thousands of households in Puerto Rico as authorities admit they have struggled to accurately measure the death count because of the devastation.

The authors, made up of researchers in the United States and Puerto Rico, wrote: 'Our results indicate that the official death count of 64 is a substantial underestimate of the true burden of mortality after Hurricane Maria.'

A report in October revealed that the Puerto Rican government was permitting funeral homes and crematoriums to burn the bodies of people who they say died as a result of Hurricane Maria — but those people were not counted in the death toll.

The directors say in many cases they don't know how to classify hurricane-related deaths, or whether they should send bodies to the central institute certifying official hurricane deaths, the Institute of Forensic Sciences.

Fallen trees cover the roads in the Miramar neighborhood of San Juan, Puerto Rico after Hurricane Maria made landfall

The ferocious storm tore through the country last year, leaving homes destroyed and roads flooded.

The country was thrown into chaos with the electrical grid being wiped out and entire communities cut off for weeks.

Officials in Puerto Rico described conditions there as 'apocalyptic' in the wake of Hurricane Maria, with widespread destruction and looting and electricity and cell phone service cut off for much of the island.

Luis Torres takes a break from sweeping debris in front of his mother's home after it was heavily damaged by Hurricane Maria

Aftermath: Hurricane Maria left a path of destruction in this rural neighborhood in Puerto Rico

Puerto Rico's nonvoting representative in the US Congress said that Hurricane Maria's destruction set the island back decades.

'The devastation in Puerto Rico has set us back nearly 20 to 30 years,' said Puerto Rico Resident Commissioner Jenniffer Gonzalez.

'I can't deny that the Puerto Rico of now is different from that of a week ago. The destruction of properties, of flattened structures, of families without homes, of debris everywhere. The island's greenery is gone.'

Felled trees cover the roads in the Miramar neighborhood after Hurricane Maria made landfall on September 20, 2017

A view of a shattered bus stop in the aftermath of Hurricane Maria, in San Juan, Puerto Rico

Governor Ricardo Rosselló described the situation as 'nothing short of a major disaster' but said it will be some time before the full extent of the damage is unveiled. Pictured is a gas station in the capital of San Juan