Facing mounting evidence that Puerto Rico has vastly undercounted the number of people who died because of Hurricane Maria, Gov. Ricardo A. Rosselló on Monday ordered that every death on the island since the calamitous storm be reviewed.

Officials will look again at all deaths attributed to natural causes after the hurricane, which made landfall Sept. 20 and knocked out power to 3.4 million Puerto Rican, as well as to hospitals and clinics. Parts of the island are still without power almost three months later, and the power grid is operating at only 70 percent of capacity.

The prolonged blackout hampered critical medical treatment for some of the island's most vulnerable patients, including many who were bedridden or dependent on dialysis or respirators. But if they died as a result, the storm's role in their deaths may have gone officially unrecorded.

"This is about more than numbers, these are lives: real people, leaving behind loved ones and families," Rosselló said in a statement.

The governor acknowledged Monday that the death toll "may be higher than the official count certified to date" — an apparent about-face for his administration, which has spent months stubbornly defending its counting method, even as it became obvious that it did not reflect the unusually high death rate in Puerto Rico after the storm.

Several news organizations, including the New York Times, conducted independent analyses and found that the number of deaths traceable to the storm was probably far higher than the official count of 64.

The New York Timese_SSRq review, based on daily mortality data from Puerto Rico's vital statistics bureau, found that 1,052 more people than usual had died across the island in the 42 days after Maria struck. The analysis compared daily figures for 2017 with an average of figures for the corresponding days in 2015 and 2016.

Puerto Rico's Center for Investigative Journalism reached a similar estimate, that 1,065 more people than usual had died in September and October. CNN compiled figures from half the island's funeral homes to report that funeral directors believed that 499 more deaths than the official count were tied to the hurricane.

Official mortality figures from all causes on the island are revised often as the government obtains more information about events after the storm. Since the New York Times published its analysis on Dec. 8, Puerto Rico has recorded seven more deaths that happened in September and 31 more for October.

Methods for counting storm deaths vary by state and locality. In some places, officials include only direct deaths, such as people who drown in storm floodwaters. Puerto Rico's method is not that restrictive; the medical examiner includes some deaths indirectly caused by a storm, such as suicides.

The leading causes of death on the island in September were diabetes and Alzheimer's disease, Puerto Rican government data show. But there was a sharp spike — by 50 percent — in the number of recorded deaths from sepsis, a complication of severe infection that can be tied to delayed medical care or poor living conditions.

Reviewing the circumstances surrounding each death will require interviewing family members and doctors who signed death certificates to find out if, for example, a heart attack might have been brought on by stress from the hurricane, or might have been fatal because an ambulance could not get through debris-blocked streets in time to help.

Harry Figueroa, a 58-year-old teacher, died in Caguas on Oct. 4 from pneumonia, and his family blamed the power outage for his death. His daughter, Lisandra Figueroa, said her father was obese and needed the help of a CPAP machine to keep breathing safely while asleep, but it would not work without power.

"Between the dust, the rain and the heat, he kept getting sicker," she said.

Lisandra Figueroa, 30, was skeptical that the government could adequately investigate all the cases like his on the island.

"I don't know if it will be possible, because of the chaos in this country," she said. "I don't know how they're going to do that. They're going to have to request autopsies of all the bodies."

That would no longer be possible in many cases. In the first four weeks after the storm, Puerto Rico authorized 911 cremations of people whose deaths were attributed to natural causes.

Rosselló had previously said that his government would look into questionably attributed deaths reported by the media. Pressure mounted last week when two Democratic members of Congress, Nydia M. Velazquez of New York and Bennie Thompson of Mississippi, asked the Government Accountability Office to review the hurricane death toll in Puerto Rico and the U.S. Virgin Islands.

On Monday, the governor said he welcomed the published reviews of the death toll, but he cautioned that the government could not adjust its official mortality count based on "statistical analysis."

"Every life is more than a number, and every death must have a name and vital information attached to it, as well as an accurate accounting of the facts related to their passing," he said.

The death toll can be a metric of economic development: Poorer localities tend to have more deaths and fewer economic losses after disasters than wealthier places, according to John Mutter, a professor at Columbia University who studied deaths from the 2010 Haiti earthquake and Hurricane Katrina in 2005.

"It's a measure of how well you protected your people, and Puerto Rico is in this odd position where it's not a state, their people are citizens, and were it a state, it would be the poorest state in the nation," he said.