Hurricane Maria killed more than 4,600 people in Puerto Rico, 70 times the official toll, according to estimates in a Harvard University study.
A third of deaths after September’s hurricane were due to interruptions in medical care caused by power cuts and broken road links, researchers say.
The Puerto Rico government said it “always expected the number to be higher than what was previously reported”.
The official death toll stands at 64.
But experts say an accurate count was complicated by the widespread devastation wreaked by the storm.