It’s officially the start of the 2018 hurricane season, but the effects of last year’s hurricane season are still being felt today, especially in Puerto Rico.

Hurricane Maria, which devastated the island, killed 4,654 people when it hit last September, according to a Harvard study released Tuesday. The official government count is 64.

Harvard’s T.H. Chan School of Public Health determined the number by surveying over 3,000 households in the country, USA Today reports.

Researchers believe that the number may be much higher than their report.

“Our results indicate that the official death count of 64 is a substantial underestimate of the true burden of mortality after Hurricane Maria,” the study says.

Puerto Rico’s governor, Ricardo Rosselló, told CNN that there would be “hell to pay” if the government kept mortality data.

“We had established that this number was going to be much, much higher than what we had as an official tally,” he told Anderson Cooper. “It’s not sticking with the number. It was just establishing that the process that we had prior led us to that number, which is what we got from doctors and death certificates.”

The country has faced many challenges since Hurricane Maria made landfall on Sept. 20.

The island has been hit with multiple blackouts and over 11,000 people are still without power. It may take up to two months for power to fully be restored, according to CBS News.