Officials in Puerto Rico say that 64 people lost their lives after Hurricane Maria slammed into the island in September. A new report says that estimate is off — by about 4,600.

If the analysis is correct, it means that for every hurricane-related death that’s currently on the books, another 70 fatalities have gone uncounted.

“Our results indicate that the official death count of 64 is a substantial underestimate of the true burden of mortality after Hurricane Maria,” researchers concluded in a study published Tuesday in the New England Journal of Medicine.

This isn’t the first time people have questioned the official number of deaths that ensued after the then-Category 4 hurricane made landfall on Puerto Rico on Sept. 20, 2017. The study authors noted that several “independent investigations” put the number “in excess of 1,000.”

One of them was by Alexis Raul Santos, a demographer at Penn State University, and independent researcher Jeffrey Howard. In November, they concluded that Puerto Rico had experienced an excess of roughly 1,100 deaths in the wake of Hurricane Maria.

The new study adds to “the growing consensus that the deaths have been undercounted,” Santos said.